The rubber band thing works by "snapping you out of" the thought :-) It's kinder to yourself to just replace it with a good one?
I invented 3 guys in togas with a Greek Corinthian column and when I caught myself putting myself down I'd yell in my head, "Support!" and they'd come running in from one side/ear and put it up in the dome of my head and then run off toward the other side/ear

I loved it and it worked fine, would get me smiling and feeling loved and supported by myself.