Am I overconfident about my writing abilities?

Many writers never ask themselves these questions:

"Where do the words come from?"
"Why one story and not another?"
"Why does what sounds good, sound good?"

https://www.youtube.com/watch?v=c2oTkLwDKEQ

The answers more or less tie in to our subconscious mind, which is infinitely more powerful and vast than our conscious one. Christianity did a terrific job describing it as the "Holy Spirit", a force that works through you. The source of your creativity isn't you.

When you realize that, you realize that you're really just an open doorway, and as you become a better writer you really just become a better and more open pathway to this source. There's definitely pride to be had but the best writers know they're a middleman between words on paper and something much greater than themselves.

So I hope that addresses your confidence issue. As for how best to develop as a writer, you do so by developing as a storyteller first. Learn, study and master the application of premise lines. Stories have a real structure, even if it's not visible to most readers. The word for "appealing to people subconsciously" that you're looking for is called 'resonance'.

"Drawing on the Power of Resonance in Writing" by David Farland is well worth a read.

George Lucas is a master storyteller. But most everyone only sees the result, not him at work. Here's a transcript of him, Spielberg and Kasdan sitting down and thinking up one of the greatest films ever made:

http://maddogmovies.com/almost/scripts/raidersstoryconference1978.pdf