Ok, so whenever I'm working on something and I actually like it I usually end up realizing that certain parts sound similar to songs that are already out there. When that happens I just scrap the entire piece because I feel like I'm stealing. Should I feel guilty about that? I feel like that's the main thing holding me back with songwriting because I always think that it's bad unless it's 100% original. But because of that, I've only actually completed one 'song' if you could even call it that. Even with drum loops and patterns I feel like I'm stealing even though lots of loops are pretty generic no matter what. I also keep coming up with excuses like this as to why I don't finish songs. Which sucks.
Then why do I feel like I'm stealing and just drop whatever project I'm working on at the time when I realize it sounds similar?
Because many ideas have already been expressed, and the stuff you come up with sounds similar to what's already been released a while ago. Don't feel bad. Just find a way to make your stuff noticeably different, whilst still retaining as much as possible from your original idea.