In the past all my projects have been constrained by time; usually a summer, a semester, or (for my undergraduate thesis) an academic school year. This means that there is very little to loose, because it's obscene to expect that anyone gets results in 3-9 months. If you do, you're lucky. If you don't, you learn from the experience and that's what it's mainly about anyway at the undergraduate level.

Graduate school is going to be different, though. In graduate school, there's going to be time to see through a project to completion. I'm not going to abandon my babies half-finished. Of course, there's the whole idea of never really completing a project...and always having a follow-up project, but there will be five, maybe more years to make it work. And this is exciting and scary, because you never really have the excuse "oh I didn't have enough time to make it work."

It either gets finished or abandoned, I guess.