Don't worry that there are always better people. Everyone, at every level, knows better people.

I know Nobel Laureates who moan that the work they did wasn't anywhere near as great as the work of Lawrence, or Einstein, or Feynman.

Hey, a B+ Nobel Prize is plenty good enough. And so is a 3.5 GPA.

You have a great attitude. Try not to be too impatient.

Here's an article in Forbes that lists important qualities that most undergraduates don't know: Intelligence Is Overrated: What You Really Need To Succeed. You'll note several important aspects that are often not mentioned: emotional intelligence, moral intelligence, body intelligence.

You specially mentioned "maturity". I recall when I first realized that a friend of mine was more mature than I was. That was a great insight that deeply affected my life. Never before had I striven to improve my maturity, but it proved to be very important.So you are already on the way.