Here's a sketch I did in high school. I never finished it and I have no plans to. But I hold onto it because I like it. And I had fun doing it. And I learned a lot from it. So, it really doesn't bother me that poor girl still doesn't have a foot!
When it comes to creativity, there is no rule that says you have to finish everything you start. Just be sure to hold on to those unfinished projects, though. A quick glance at one may be all it takes to get your creative juices flowing again when you get stuck.