Photoshop is so big, so massive that even being with Photoshop for several years, I am still learning everyday. I am by no means an expert, so for that reason, I continue to push my skills further everyday. How many other here do the same? I suspect many many here on deviant art.
For me, I use a combination of tutorials, blog posts, and pure playing around. Not every piece is going to be a home run, but I feel I am getting closer.