[Joeri]

Teach. Find people to mentor, find user groups to present to. There is no better way to learn more about subjects you're superficially familiar with than to teach them. Pick subjects where you think you're an expert, and prove to yourself that you weren't, or pick subjects that you would like to know more about and try to understand them well enough to explain to someone in 45 minutes.

You will be terrible at this at first, but teaching is also a skill that takes lots of practice to acquire.

I would also agree with what others said: stop comparing yourself to others, no good will come of it. There is always someone better, there is always someone worse. It doesn't matter. Set a standard for yourself and meet your own standard.

P.S. If you're looking for a good resource to learn presenting from, I would recommend macsparky's presentations field guide.

[ghubbard]

If you want to teach without leaving the house or standing in front of a group of people, try http://exercism.io/ (Open Source and free).

Solve simple coding problems, review the submissions of others and help them become better coders. Trying to clearly explain concepts to others is the best way to make sure you really know them yourself.

This is also something that you can do for 10-15 min every day, which will add up over time. Ask for feedback on your own solutions and find out ways others think you could improve things.