I very rarely use photoshop anymore -- but for the benefet those that want to learn i
1) Explore, 2) Welcome mistakes, 3) Breathe, 4) Recognize it's an unknown and approach it with curiosity, 5) or don't... do whatever it is you feel you must.
In November of last year I started "rock climbing" at an indoor gym. I remember at first I had absolutely no idea what I was doing. I attacked the wall with my arms and payed little attention to my legs, body posture, breathing, technique, how to read the holds or anything of value ;-) It was frustrating until I recognized I was a beginner and accepted that being a beginner means you don't know. Expectations lead to frustration, so be kind to yourself and address where you are, not where you want to be.
I taught myself Photoshop. I still recall how daunting it felt. It's an application that offers what seems like infinite path ways to an unknown result. My problem was I wanted to know where I was going and how I was going to get there. Nevertheless it was my problem that propelled me into PS and made me read through forums, books, watch online videos, ask questions and most importantly experiment over and over and over and over and over, etc... again. Practice makes perfect. Übung macht den Meister.
Shoot RAW! This is how you're going to get to work and rework that image over and over until that "something" clicks. I second Andrew's recommendation: Lightroom. The edits you make are non committal and non-destructive, so you can always go too far and come back, and in the process learn something. Use the tools therein and observe their effects using the history palette. Get acquainted with it.
After Lightroom I still use PS for curves (local and global corrections), layer masking, cloning/healing, sharpening, dealing with noise, photo filters and that's about it.
In the end through trial and error you come to know what works for you and PS becomes another language you speak. It's a beautiful tool. Have fun, or not ;-)
JJ