It is a common fact that people wear social masks when interacting with others, depending on the situation they find themselves in. People do not talk to police officers the same way they talk to their boss, or their own family. There are certain expectations that are a part of the social contract which require fulfilment, such as smiling brightly while dealing with customers even if you are tired and your feet hurt, or treating those who are higher in the hierarchical status or authority with respect and compliance. Failure to fulfil the requirements of this contract may result in detrimental consequences for one's being. It can be quite humiliating to reduce yourself to a set of smiling teeth and kind, though fake, words being spoken.
For some, this daily ritual of self-humiliation gets tiresome. It is not much of a surprise to realise many people escape to roleplay as a form of self-care, and there are plentiful ways to do that - from playing an MMORPG, actually LARPing, to even reading fiction. Life seems somehow better, exotic even, when one can self-insert as someone else, in a fantastical land or with magical powers.
This perhaps gives insight into why many people resort to BDSM. It provides a safe way to be stripped of (pun very much intended) any societal expectations - you are a maid, a slave, a pet, a fucktoy, a master, a dom. You now have clear rules of engagement, and nothing outside of them is expected or even encouraged. Many submissive people claim it is 'liberating' to submit to another human being. What they mean is liberty to become what they want to be, at the very core of their carnal desires. Suddenly, the social self-humiliation for very little reward (as it is expected to just grin and bear it) and many repercussions turns into humiliation from, or onto, another, for the gratification of both parties involved. The utter ecstasy in physical pain, whether inflicting it or having it inflicted, reminds both of their own humanity, be it fragility and vulnerability or sense of power and the need to control. At the very height of such shared moments, one could argue the reasons for engaging are completely different depending on the role, but what it all could boil down to is regaining a sense of self.
Problems arise when a sense of self is not established in the first place. People who engage in BDSM should be of sound mind, and not seek such treatment as a way to remedy their own ailments. There are far too many "doms" who are just looking for a way to abuse, and "subs" who are trying to re-live their traumatic moments in a somewhat controlled environment. There are also far too many stories of people just going to another's house to meet them for the first time, get naked, do the deed, then leave home. Our minds understand that what is happening is desirable, but our bodies do not know that. Our bodies have a mind of their own, and they remember the experience as abuse, not as a fun little exploration. In addition, when no sense of self is pre-established, it is very easy to get lost in the sauce. Letting go of daily self is only healthy if there already is a daily self, a self to return to outside of BDSM. We are human, therefore we have our own principles, desires, ambitions, flaws and needs, regardless of others. It might seem like a selfless act to fully submit to another, but it is false martyrdom usually involving garden variety of mental illnesses that should be treated properly, not perpetuated. In other words, sometimes one does need an ounce of self-respect to say "fuck no".
The uttermost important part of any BDSM session is the after-care. After all the degenerate stuff is done, the body needs to know it is okay. It is not in imminent danger, and the person who inflicted all those horrible, yet very much desired, actions is not a threat, but a loving, caring partner. The brain needs to convince the body of that, and what better way to do so than cuddling naked, skin-to-skin, under a dim light? Doesn't everyone want to hear "You are such a good girl/boy."? It also provides the dominant one a way to simmer down and to humble oneself from the power high they might be experiencing, so this dynamic does not spill over into other aspects of relationship.
In conclusion, an amazing way of self-care is leaving your "self" at the bedroom door, and taking on a persona that does not align with your presentable self, and all is well as long as you come back to it better and more satisfied than before. If there is nothing to come back to, you are a one-dimensional side character in someone else's life, and no one really likes those. Everyone has problems, but it is our duty to fix them before we let anyone else even try to do so, to hell with Saviour Complex.