I find myself sometimes thinking of my(past/future/criticism-receiving)self as a separate person because it reframes my treatment of that person. Sometimes I give the next guy a gift by cleaning shit up or otherwise preparing stuff to make his life easier, and thank the last one for his gift.
I have been doing that and it really helps! Self criticism becomes much more human and empathetic when I realize that I can accept the things that I find wrong in myself in other people