I broke up with my EXABF about two months ago. Letting go is the one thing I struggled with. Fortunately, during this painful and confusing period in my life, I also sought professional help. Through therapy, I have realized that many of the reasons I was holding onto this relationship had NOTHING to do with my EXABF. I felt that my EX was the love of my life, and I don't know what the future holds, but I do know that what kept me clinging to this relationship were my own personal insecurities, my feelings relating to abandonment, and my feelings about my alcoholic father. I genuinely loved my EX, and possibly still do, but it drove me crazy that I couldn't let go of someone who repeatedly demonstrated how little he loved me. When I got to the root of my issues, letting go was less of a struggle.
Don't get me wrong, I still think about him every day, but I don't long for him as i used to. Breakups in general are difficult, but breakups with addicts are even more complicated. Nothing makes sense if you focus on the addict's behavior, the answers are within ourselves.