Boredom is the most common trigger for relapse, according to Anna Lemke anyway.
People refer to dopamine as "the happy chemical" and while that's not untrue, it's reductive; more accurately, dopamine deals with motivation and reward. It's responsible for making you feel rewarded for doing things, and making you want to do things that make you feel rewarded. With that in mind, it makes sense that the opposite of a high dopamine state isn't sadness, it's boredom.
Find shit to do. Ideally something that feels rewarding and exercises your drive to create. Find ways to biosynthesize dopamine instead of getting it off the shelf. Doing nothing just depletes willpower.