I was extremely lucky to get to work one-on-one with someone much more experienced than me when I was starting out. I interned at a startup and was making the iPhone app with one of the original engineers.

I had already gotten pretty good at the slamming my head against things until they work part. So I could eventually make something that functioned, but my code quality was terrible.

Where having a mentor really helped was becoming more disciplined, seeing good code, and learning new tools and services.