Hi Anchorage,
I've done a bit of that in the past myself - I'd have to say for my part that it depends and usually it goes down in one of two ways:
1. sometimes I've tried to clear the air in order to change things (usually to make me feel better by making the other person think that I'm less of a no-good waste of space

) and when that change has not happened, then it's felt like a bit of a waste of time.
2. at other times (and the way I try to do it nowadays), I have been very clear that the reason for clearing the air has been so that I can be honest with others about my behaviour and I have accepted that it may not change their view about me at all - in those circumstances I feel a lot better as a result.
So in my experience when I have no expectations from the process other than honesty and openess, so that others can then be free to choose their own response (whether I like it or not), those are the situations where it seems to work well for me.
P.