At least part of the desire to ctb almost always comes from feeling trapped.
(self plug)
- I am trapped in this job - I can't get a better one and it's miserable. But I have to stay here so I can pay my bills.
- I am trapped in with this illness/disorder (physical or mental) - and I can never get away. It will always ruin everything.
- I am trapped in this relationship / with these "friends" / with my family - no one else would ever love / understand / listen to me like they do, even if they are toxic and/or hurt me.
- I am trapped in this body - I'm not smart enough or good looking enough, so I have no opportunity.
- I am trapped in this mind - I am too anxious and will always mess up any opportunities.
- I am trapped in this world - the way things are, by default, is bad, and I'm powerless to affect it.
- I am trapped in this house - I am dependent on people and could never provide for myself (or I "won't" for whatever reason).
- I am trapped in this room - the outside world is frightening, and people may hurt me. I don't like them. I don't want to be near them.
- I am trapped in this existence - no one will let me ctb.
It's why I find pro-life absolutism and our mental health emergency system to be so offensive. By taking ctb off the table and telling someone it is not an option, you are re-enforcing this feeling of being trapped.
So, for you, when you choose to ctb, my guess is you're basically opening the cage. Ctb will free you from whatever is making you feel trapped. So, you decide to ctb, the feeling that motivated you to ctb is - by default - eliminated, because you've chosen a path that eliminates the concern.
It is difficult. Survival instinct is incredibly hard to overcome, and this is one of many reasons.