[Kiwi_queen]

I think it depends on what happened. If the friendship were lost over something not very "serious" (ie: a fight over something trivial just happened to escalate to major catastrophe) then I would go back to change it. But if the friendship had been lost over something "serious" (ie: they betrayed you to your enemy or they cheated with your s.o.) then I wouldn't change it because I would know that they weren't really my friend to begin with.
As for reliving it, I wouldn't because it's better just to move on and forget it.