I deeply psychologically struggled with exercise for most of my life.
part of what's helping me now is testosterone (primarily because it reduces my fatigue which was the main factor for me not being able to do much physical activity, but also because it makes it feel safer to experience the physical reality of my body, being aware of my body is not as stressful.)
another thing that's helping, though, is the realization that exercise does not require bodily surveillance and measurement in the way that I'd been trained since childhood.
I get very distressed by the numbers associated with exercise--how many repetitions, how often, for how long, etc. I get distressed with these numbers leading to comparisons and thus value judgements (e.g. "I did this exercise 25 times two days ago but now can only do 15, I must be doing 'worse'")
but a breakthrough for me was that exercise doesn't actually require any numeric component. it doesn't matter how frequently I exercise, for how long, or how many repetitions of anything I do. I can literally just move my body until it doesn't feel good anymore or until I just don't want to, and then stop. I don't have to count anything or record anything. If I want it to just be pleasurable movement, it can just be pleasurable movement.
another thing that helped was to prioritize exercise around things that will make it easier for me to do stuff I want to do (rather than prioritizing what someone tells me I "should" do). For example, I have a hard time sitting up straight, which leads to back pain, so I've started working muscles that help me sit up without as much effort.
making exercise into something directly practical ("if I do this tonight, it'll help me tomorrow, like the same principle as getting water before bed so I don't have to get up in the night") instead of vague and abstract ("I feel like I should exercise to 'be healthy'") has helped me.
Now I feel like I'm just doing a thing to feel good in my immediate future instead of endlessly working towards an elusive goal I can never reach.
anyway, idk if this is helpful for anyone else, but sharing just in case. it took me decades of life to be able to shift how I understand the purpose of "exercise" enough that it doesn't immediately flood me with feelings of low self worth and hopelessness.