Do you think it ever works to get back together with someone you once dated? If so, what are the circumstances under which it can work out?

For example, maybe you and another person really hit it off, but you live in different states, so the timing is bad. You try to make it work long distance, but it just fizzles. Or maybe one or both of you are pursuing education and/or career, and the timing is bad for that reason and it fizzles.

I know that conventional wisdom is to not get back with an ex (and I agree from what I've observed), but I wonder if there are indeed exceptions.

Also, what about if they weren't actually an "ex," but rather someone you went on a few dates with or were starting to get to know, but then timing or circumstances were bad. Does starting a relationship/starting to get to know someone when circumstances are bad tarnish it indefinitely? I know it's hard to go back and re-build once you've gone forward on a poor foundation...or maybe that isn't right. I'm curious for your thoughts.

Thanks in advance!