Here's the thing... you recognize it is unhealthy, and yet you continue.
You say you want to change or let go of it, yet you are holding onto it.
In order to let it go, you have to let it go. You can't wait for someone else to come along and substitute that person for the one you are feeling emotion towards. You won't even see the next person until you accept your situation and you decide to move on.
It isn't what I might do, or others, it is your decision. And that is the ONE thing we do have control over... our own choices. You are choosing to hold on. Figure out why and you'll move on.
As they said in The Matrix "You can never see past a decision you don't understand." Understand what is holding you back or you are afraid of in the future, and you'll have already moved on.