Long story short:
One of the main things that happens to a target of abuse is that the person is "taught" or conditioned to put something else before their own self-care.
We are born with natural boundaries and automatic self-care and self-protection.
In other words, in our natural, healthy state, we protect and care for ourselves first, automatically.
Picture putting your hand in a jar of hornets; your instinct would be to NOT put your hand in.
Picture standing at the top of a sheer cliff, your instinct would be to keep yourself balanced and safely far enough away from the edge.
Those examples are extreme, however with abuse, those automatic instincts to self-protect are slowly reversed, kind of like turning a fleece-lined raincoat inside out. The protection against the weather is going the wrong way, it's like it's protecting the WEATHER from YOU, but you are not being protected from the weather~
(...don't ruin the metaphor with semantics about the raincoat still protecting you from the rain, technically... you get the idea, the rubber or plastic is not where it's supposed to be, doing what it's supposed to do).
With a dysfunctional, codependent or abusive situation
(it doesn't have to be purposely neglectful or abusive, it could be situational, like an ill family member, trauma, a death, or a divorce),
"conditioning" takes place; the target is slowly conditioned (or brainwashed if it's abuse) to lower their boundaries and put their own self-protection instincts LAST instead of FIRST. After a while, not only is the raincoat turned inside out, but it's taken off and hung up in the closet, or tossed on the floor. It's not gone completely; boundaries can be rebuilt and healed, they're as real as any other part of us albeit not visible. However, without a raincoat at all, the weather hits a person directly with no barrier in between, and the person has been conditioned to accept this as if it's the "right" thing to do. Without boundaries, others will encounter no resistance or rebellion when they invade a person's space (physical, mental, or emotional), and that's the reason for the conditioning.
Along with the lowering of the boundaries and putting one's needs LAST comes putting something else FIRST. The original intent for this would be for the target to put the needs, wants, and comfort of the controller/abuser before their own, no matter how trivial. However the effects of this are on the target, not the Controller, so that means "putting something else before my self-care, self-protection and needs" remains as a program in the target's subconscious, whether the abuser is present or not.
So apply that "program" to using substances or other things to deal with stress, anxiety, or depression. The FILTER for moderation or for the rejection of something being ingested, or for stopping before something has caused damage has been turned inside out, or discarded. So the body and mind don't automatically reject ingesting something or doing something polluting or destructive to one's self. The person puts the substance or the behavior AHEAD of their own self-care and self-protection, just like they put everything else before their own self-care and self-protection.
Even playing hooky from work or school, or being late falls under this "program". Keeping the job, doing it well, and keeping up one's work reputation IS "self-care" and "self-protection", as is doing well in school and maintaining good grades. So when we have that program running in our subconscious, when something falls under the category of being "good for me, my well-being, and my prosperity", it gets "rebelled against" automatically; that's part of the program. If it's something that's "not good for me", it gets put on the top of the to-do and the okay-to-do list.
It's much more like a program than a thought process, and it makes us run our priorities backwards. To de-program ourselves, it is very important to focus on healing ourselves and restoring our BOUNDARIES. Think of them as being very much like the organ known as skin (not spikes or brick walls), and you're halfway there.
Further, this "program" also includes our children and others close to us. If we have healthy boundaries and relationships, then our natural self-protection/self-care mechanism extends to those in our "personal circle", without being controlling toward those individuals. So we automatically protect and care for them as well. That's NOT the same as putting others ahead of our own self-care, that's PART of our self-care.
Remember the oxygen mask instructions on a plane: when they drop down from overhead, we put them on ourselves first and then on our children, loved one, or other persons nearby who need help. We put them on ourselves first AND we protect and help others, not "instead of" helping others.
In the oxygen mask scenario, this aforementioned "program", when it comes to our children, partner, and others, might look either like: We put the oxygen mask on THEM FIRST, no matter how long it takes, and risk letting ourselves pass out (then we can't help anyone at all),
OR it might look like: We help OTHER PEOPLE put their oxygen masks on first, BEFORE or INSTEAD OF putting ours on, or helping our loved ones put THEIR masks on. So not only are we putting someone else's needs before ourselves, we're putting someone else's needs before our LOVED ONES.
Again, that's that same "program", it just depends on how our subconscious is interpreting "Self"; including our loved ones, or not including our loved ones. So it really is an important and essential process to uninstall this destructive program from the subconscious. Not with shame, or self-flagellation, those things actually activate the program. It needs to be removed with the intention and goal of caring.
Locus Of Control