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There are two types of prisoners, one being far crueller than the other: a physical one within the confines of a prison, where it is iron shackles that restrict freedom; and the second, which is an inner one, where the heart is confined by desire, whose shackles of obsession are far more painful and limiting than those of iron.
A prisoner of a physical jail, if his heart is free, can be in spiritual bliss. Indeed, some of the most celebrated books in the Islamic library were authored behind bars: al-Fatāwa al-Masriyya and Iqtidā Sirāt al-Mustaqīm by Ibn Taymiyyah, Fī Dhilāl al-Qur’ān by Sayyid Qutub, and al-Sarkhasī authored al-Mabsūt in the Hanafi Fiqh in 20 volumes.
As for the prisoner of desire, whilst free to traverse the Earth, every aspect of his existence is undermined – sleep, health, focus, clarity of mind, spiritual wellbeing, and so on.
Ibn Taymiyyah said:
المحبوس من حُبس قلبه عن ربه و المأسور من أسره هواه
“The true prisoner is the one whose heart has been imprisoned from his Lord, and the true detainee is the one who has been detained by his desires.” 
Whether this prisoner is at work, with friends, or at home, awake or asleep, the object of obsession never ceases to hover before his very eyes.
When asked about his/ her absent-mindedness and cause of pain, it’s always the same answer:
“I’m in love.”
Love, however, is supposed to be a cause of strength, to inspire proactivity and give rise to a brimming smile, both outwardly and inwardly. These are the outcomes of love, or in Arabic, mahabba, which generally has positive connotations. If such ‘love’ renders one frail, distracted, or sleepless, then it is nearer to the Arabic concept of hawā (desire), which generally has negative connotations.
Taking a closer look at the word hawā, Ibn Fāris said that the three letters of hā, wā, and yā (هَوِيَ), when they come together, imply two meanings: خلو emptiness and سقوط plunging. 
As for the first meaning, emptiness, the space between the sky and land is called Hawā in Arabic, because it is empty. Similarly, Allah describes the hearts of people on the Day of Judgment:
“..and their hearts are void (hawā’)”  …
…unable to compute anything because of the terror. And as for the second meaning, plunging, the Qur’ān describes Hell by saying:
وَأَمَّا مَنْ خَفَّتْ مَوََٰزِينُهۥُ
“And as for those whose scale is light”
“Will have his home in a pit (hāwiya)”  …
…as its inmates will plunge into it.
It is for this reason that desire is dubbed Hawā:
لَِِنَّهُ خَالٍ مِنْ كُ لِ خَيْرٍ، وَيَهْوِي بِصَاحِبِهِ فِيمَا لََ يَنْبَغِ ي
“…because it is empty from all goodness, and causes one to plunge into what is wrong.” 
The darkness of the haram
“I’m just looking for happiness.”
This is usually the go-to justification in the face of advice or criticism, not knowing that those who search for it beyond the parameters of the permissible will miss the mark every time, as the very first prey of lust is happiness.
Imam Ibn al-Qayyim said,
“Whoever becomes attached to something besides Allah will suffer at its hands in this life three times: when striving to attain it; after attaining it in the fear of its departure; and when it bids him farewell.” 
Imam Ibn al-Qayyim also relates the story of a man who, as he stood outside of his home, saw an attractive woman pass by while asking for the directions to Haṃām Minjāb, the name of a local spa.
The man treacherously pointed to his home, saying, “It’s here.” She went in, only for him to follow her and close the door. Having realised the setup, she faked her delight and said, “We should bring something to make this evening most worthwhile.” He left in an excited hurry, promising her to bring all that she likes, but forgot to lock the door.
Upon his return, he found that she had ran away. The man lost his mind and came out into the streets looking for her, saying:
يا رُبَّ قَائِلةٍ يَوْ م ا وَقَدْ تَعِبَتْ أَيْنَ الطَّرِيْقُ إِلى حَمام مَنْجَابِ
“Where is the woman who once said, ‘Where are the directions to Haṃām Minjāb?’”
Later on in life, as he experienced the throes of death, those around him urged him to say “lā ʾilāha ʾillā Allah” – for people will be resurrected upon their last actions – to which he responded:
“Where is the woman who once said, ‘Where are the directions to Haṃām Minjāb?'” 
He repeated it over and over again, until his soul departed. Are such relationships and endeavours a heavenly pursuit, or a hellish nightmare that are to be fled from?
Those who wait until marriage for sex suffer a fraction of the divorce rate as compared to those who do not, because those who engage in it outside of marriage find that the experience imprints on them much more than the individual does, so they live the rest of their lives trying to recreate that initial experience, chasing a memory in vain.
Those, however, who limit their sexual encounters to marriage will remember the individual much more than the experience, and hence their relationships are stronger.
This isn’t to say that your fate is doomed, but it will need a bit more hard work, similar to those of low metabolism; they can still get to a healthy weight, but will require greater effort than those with high metabolism.
I remember a lady who led a self-confessed unchaste life saying that, much like Velcro that eventually loses its fastening quality because of constant tearing away, she described having parts of her essence taken away after each sexual encounter, until she now feels soulless.
Indeed, how can you become a wholesome human being if you had gotten with x individual, then ripped away, then with y individual, then ripped away, with countless people having walked away with pieces of you? Your ability to respond positively to commitment and marriage later on in the future will deteriorate so long as this type of behaviour is not put an end to. Particularly for women, the levels of oxytocin – called the “love hormone” – that is released during intimacy, into the bloodstream and that which helps women connect, are released in lesser and lesser amounts, the more sexual partners she has had. 
Which of the two is happier? Is it s/he who pursues a relationship outside of wedlock under the cover of night in order to spend a short-lived moment of pleasure that’s followed by excruciating guilt and piercing pain? That is because they realise – as a Muslim – that the Prophet (ﷺ) had seen the fornicators suffering inside of ovens within their graves; and having recalled Allah’s description of fornication:
“And do not approach fornication. Indeed, it is ever an abomination and is evil as a way.” 
During their intimate moment, should someone knock on their front door, they may both leap in fear as their conscience has already been terrifying them about what they’re engaging in. Then, should she get pregnant, it’s further gloom, which, in many cases, is followed by abortion, which only compounds the gloom and furthers their sorrow.
Is this person happy? Or is it the one who distances himself from the prohibited, finding strength in salāh, du’ā, Qur’ān, knowledge, the masjid, and good companionship, patiently awaiting the arrival of that righteous spouse who marries them publicly?
During their wedding, families are happy, gifts are offered, smiles are exchanged, and happiness is all around. Later on, should they be intimate with one another, their consciences are at peace and their hearts are at bay, knowing that what they’re engaged in is pleasing to Allah, not angering, as they recall the hadīth:
“…and cohabiting with your spouse is considered a charity.” 
Should someone knock on their front door during these moments, they remain unfazed in the least. Why should they be? They aren’t doing anything wrong.
Then, should she become pregnant, their happiness is only furthered by the prospect of children who will be an extension of their Islamic legacy.
Then, when she delivers, an ‘Aqīqa feast is arranged, and – once again – families are happy, gifts are offered, smiles are exchanged, and happiness is all around.
Which of the two are happier?
Part 1 | Part 2 | Part 3 | Long-Read
 al-Wābil al-Sayyib
 Maqāyīs al-Lugha
 al-Qur’ān, 14:43
 al-Qur’ān, 101:8-9
 al-Jawāb al-Kāfi
 al-Qur’ān, 17:32
 Muslim, on the authority of Abū Dharr
Beautiful reminder and much needed for someone who’s struggling to move past a haram relationship even after repentance. Jazak Allah khair.