I'm only recently off adderall, like within the last month, and I know that one of the best ways to stimulate my dopamine system is to exercise, but like all of us it's very hard to motivate myself. I still have not done that first day's workout I had written down in my day 1 goals...
But now I am showing some progress with a "baby steps" approach in which I set a small goal for myself, and if I really don't have the energy to do it, then I make the goal smaller, and so on until I at least do something, even if it is just a single sit-up or to jump up out of my chair instead of simply standing.
The point is to actually getting a starting point somewhere, no matter how small, and work up from there, and always make an effort to push your boundaries, but never beat yourself up when you don't exceed expectations or when you take a step backward. The hardest thing is not criticizing myself for "just doing 10 push-ups" or JUST anything, and recognize that it's better than the alternative of procrastinating yet another day...
This technique is how I quit smoking, and while that took me over a year and a half, it worked where no other method had. And if this doesn't work for you, maybe the bigger lesson is to find something that does, even if you have to invent it or you feel silly doing it. Just be open to experimenting and having a positive attitude!