[iammjm]

Don't compare yourself to others, instead think about where you were X years ago vs. now and recognize the progress you have made.

As for successes of other people - the fact that they succeeded means success is possible, likely also to you. Learn from successful people by studying their stuff and the ways the go about things and see if you can apply those lessons to the domain you want to excel in.

All that being said, also remember this: its OK to be mediocre and most of us are. In the grand scheme of things, we are just a particular incrustation on some edge of a possibly infinite fractal structure... don't let this stop you from trying to be great, but also don't let the self-imposed pressure kill the everyday joy of doing stuff and just being a human. Good luck and have fun