My trading breakthrough was when I realized "trading is not rocket science".
Yes, you can make trading extremely complicated, but I having the most success with incredibly simple trades. Over and over again.
My second breakthrough would have to be learning and being comfortable with "just pulling the trigger".
I had some issues with complicating the trade, looking for proof I was correct, etc. Basically I just have to be somewhat sure its a good trade, then pull the trigger, and if its right I make money, if its wrong I close the trade. Just do it, works wonders for me.