Ok here are mine:
1. Started learning how to "really" trade with Futures, the YM (mini-dow) first off. Very painful experience psychologically and made my wallet a bit more thin.
2. Read stupid books on indicators and all that. I believed that in order to win in this game you had to use an indicator and if you found a good enough indicator you would win..... WRONG
On the contrary, the smartest thing I ever did:
The smartest thing I did was learn about the psychological effects trading has on a person and finally start trading the way I wanted to trade. Going prop was the wisest dicision in my trading career.... I finally could afford to day-trade stocks.
Also another smart thing was review as many posts as possible here on ET. ET is like an archive of great and doomed traders. I picked a lot of traders that I knew had failed and are current suceeding and review all their posts, hunting for information, tips, and all of that. I print out threads that I believe are beneficial to me and I print out threads of things I should never do.
So there is the mistakes and the greats of trading so far for me
EDIT:
Also for me.... in all things in my life, things don't seem to gradually come to me. Things just sorta "click" in my mind, and I will finally understand something. For me it is usually an all or nothing kinda deal. I can't explain exactly when that click happened in my mind, but it was somewhere when I decided I needed to move to a different market to trade, and then I actually did.
Just figured I'd throw that out there for others who learn stuff in a fashion where it just seems to "click"