Ive felt that way a few times, so I feel for you. When its all consuming its hard to think of a time when it does get better.
But if its any comfort, for some of those Ive fretted over in the past, I wouldnt give the time of day today! What a total waste of time ! hehe
Others I remember fondly and whatever misgivings I thought at the time , I just remember the good times we had....and thats a good feeling.
Yet others, Ive pondered if maybe things I /they could have done differently ..and would that have shaped a different future? But crucially, we couldnt at the time..so..
Past relationships, dont rule my thoughts in any shape or form today. Just the experience of being in those relationships has given me some idea of what I need/dont need ...and the knowing that even if I get hurt/knocked back ...it gets better with time
Hang in there ...even if slowly, it gets better ((

))