If it helps, some of the most successful people I know made their achievements by taking a risk on their current capabilities. It's obvious to say, but the best way to grow is to be in a position where you have a good growth opportunity - and inherently, that means you'll be swimming in a slightly bigger pond than you're comfortable in.

I don't know anything about the specifics of your situation, so definitely discount this advice if it's not applicable - but remember that every high level / successful person had to be, at some point, wholly out of their depth in order to rise to the occasion!