I'm a bit of a perfectionist and used to agonise over any mistakes, mismatches etc. It really slowed me down and took a lot of the joy out of quilting.
Now what I do is leave the mistake until I've finished what I'm doing. If it still bothers me, I sort it.
If I can live with it (probably because it's now paled into insignificance with all the other mistakes, lol) I leave it, finish the item and move on to the next.
Although I'm still a bit fussy, I'm much happier and relaxed now.