You definitely knew what you had... and that's why you let it go

As the saying goes, "You don't know what you got 'til it's gone."

That is, until you get it back, realize what you had, then remember why you didn't want it in the first place.  

The phenomenon of romanticizing over lost relationships is one that never ceases to amaze me.  We break up, get a little lonely, and then start to jones over all the sweet goodness that we are now missing.  But our minds conveniently seem to gloss over the not-so-good things that led us to call it quits in the first place.  Or we fantasize over the good stuff so much that in our minds it starts to outweigh the bad.  Or we may even start to think that things might be different the second time around, only to realize that sh*t has not changed one bit.  

I think it is in our nature to see the good in people sometimes in spite of the bad.  Indeed it is written, "Love keeps no record of wrongs."  (1 Corinthian 13:4)  But do we really think that it is going to be all good the second (or third, or fourth, or fifteenth) time around??  We even console people during rough breakups by telling them that their foresight-lacking ex just didn't realize what he/she had.  In reality, he knew exactly what he had and decided he just didn't want it. 

By contrast, I do admire when people recognize adjustments that can be made to be happy with someone and commit to making those changes for the benefit of being together.  But that situation is a far cry from just giving it another shot because there is nothing (or no one) better to do.  Don't you think?