Whenever I've run into a situation when my feelings for someone are stronger or different than theirs are for me, I always end up asking myself, "Would I rather have them in my life like this (pain and everything) or would I rather not have them in my life at all?" This usually results in me deciding that I'd rather have them in my life with the imbalance, even if it means I get hurt from time to time. Then I occasionally have to remind myself that I chose to be in this situation, no one is forcing me and if the pain is too much, I can end the relationship. Sometimes that's the choice I make from the beginning, because it's just too hard to maintain a relationship with the difference in emotions, so to protect myself I have to cease contact and get some distance and time before the hurt heals, and then I may or may not be able to be friends with the person down the road.
I don't know if it's possible to dial down an emotion the way you're wanting, if waiting for the intensity to lessen over time hasn't worked. Why not find a mental health professional to talk to about it, though? Instead of just asking for a pill, they may have some insights or suggestions on ways for you to train your brain to focus more on the positive and being content with what you have, rather than dwelling on what you don't.
Pan Female, Hinge in a V between my mono (straight) husband, Monochrome and my poly (pan) partner, ThatGuyInBlack