Build. Build. Build.
The best advice I can give you is to constantly build and ship projects. It doesn't matter what, as long as they do things that are interesting to you.
Do not build something just because you think it will be "easy". Don't even waste your time trying to assess your skills... just start with a cool idea, then figure out how to do it.
A simple hack to build lots of projects is to use project based tutorials as a starting point. These tutorials will walk you step-by-step through building a simple program / app, but don't be content with just following along... extend the application past what was done in the tutorial. Better yet, build something else that has a similar structure but does something totally different. I've kept myself entertained for hours and really upped my skills by doing this :)