Does "not coping" necessarily mean doing something not good for yourself? If so, maybe it means that you don't know how to cope in healthy ways. I have unhealthy coping methods too, and when I'm not coping I do tend to fall back on those. But I think maybe the bigger problem is what I'm not doing - such as not speaking up for myself when I need to, not dealing with emotions directly, not using distress tolerance or mindfulness or other skills that I theoretically know since I teach them to other people.

In DBT you learn to think about what are the factors that reduce your effectiveness, because we probably don't just set out to fail. There are reasons. Such as:

Lack of skill - you actually don't know what to say or how to act or what will work.

Worry thoughts - you worry that if you do what you know you need to do for yourself, someone might not like it, or maybe you don't deserve to get what you want or need, or maybe it won't work effectively or be good enough.

Emotions - anger, fear, frustration, guilt, etc. can be so intense that the emotions control us or make it harder to control what we do.

Indecision - not being able to balance asking for too much vs. not asking for anything or saying no to everything vs. giving in to everything. Not sure what your priorities are.

Environment - sometimes skills don't work because someone else is too powerful or will be threatened or would punish you or not give you what you need, or at least not until after you sacrifice your self-respect.

Also, these things tend to build on each other and multiply the effect and make it harder to be effective/cope in a healthy way.