Am I not the happiest I can be because I am not with my ex- boyfriend?

When I get super happy and am really excited about life I suddenly come to the realization that I'm happy but not as happy as I can be because I will automatically think about my ex-boyfriend and how much I love him. I feel like I can't be completely happy without him. Its like when im really happy about life I wish he was there to make it that much better and when I cant stand life I wish he was there to lift me up becuase when I was with him I never had a bad day no matter what happened becuase he was there for me if a way no one else is or will ever be. We have been broken up for 3 years and I feel like he is my soul mate but he is dating this promiscuous girl that I know means nothing to him. I think I should let him go through this phase and see what happens ?What should I do?