Good question about gaining confidence. It helped me to experiment a lot, make a ton of studies and not worry about the results, but rather try to gain a visceral experience with how watercolor pigments interact with paper and water -- and try to figure out what I needed to change to make each element work. So my suggestion is paint a lot!

If you haven't had a chance, watch some of Olly's videos and try each thing he shows multiple times. Tons of skys, trees, aerial perspective -- not necessarily as part of a finished product, but as a exercise.

Good luck!