Every knitter probably has had at least one project which didn't turn out as anticipated. Sometimes these can be re-purposed. The itty-bitty llama hat I made earlier this year got given to a friend with a baby, and I knit another, larger one.
Back in the summer, I knit a tank-top. It's a good pattern, very popular, but it doesn't seem to have been designed for someone shaped like me. I'm not curvy enough, and I didn't realize that until I finished it. So, I wore it a few times, over a t-shirt (to preserve my modesty, and because the whole world does not need to see that much of my blindingly white skin), and then it languished in the drawer for a while. I frogged it tonight. There was about 80% of a ball of it left over, so that, together with what I frogged tonight, may be enough for a short-sleeved top.
I knit a cowl this summer, too. It matches one of my berets, as they're both in a bulky thick-and-thin yarn that ranges from yellow, to green, to brown. And I knit it much too large. So I don't wear it. It was also frogged. I want it to be a cowl, but I want one that fits. I wear scarves a lot, but I've only knitted one scarf for myself, and it's still a little too heavy, given the current temperatures. So a cowl seems like a nice option, if I can make this one small enough (but not too small, since I have no wish to be choked).
Frogging is actually rather relaxing, despite the fact that I'm undoing all that work. I guess knowing that I will can turn the yarn into something else that I'll be happy with is comforting.