There truly are no mistakes in crafting - just creative opportunities.
I've found that when something doesn't go as planned, that's the best time to start looking at what I'm doing from another direction.
Often I end up turning what I thought was a mistake into something even better than I had originally planned...
"Mistake" 1: I glued down the paper squares before really playing with them, and ended up having to remove them from the card base and rearrange them. Unfortunately, that caused some tearing of paper. Instead of giving up, I simply edge distressed everything. I think the rough edges look cooler than what was originally there.
"Mistake" 2: Originally I had wanted to incorporate this month's Stamp of the Month into the card. However, no matter what I did, nothing felt right. But I liked the squares and the colors, so I just took away that one element that was blocking me and focused on what I liked.
"Mistake" 3: I wanted to create fun clusters of embellishments, but I had used up most of the embellishment packs I had that went with the colors. The few embellishments I did have looked sort of strange floating around on the upper and lower corners, and I really didn't have anything that could ground them. So I went to my scrap stash and cut a few circles - that allowed the card to flow and the limited embellishments to stand out.
Don't be afraid of imperfections - often they end up turning your projects into something even better in the end!