Honestly, I can say that size finally caught up with me. I made 218% last year by constantly upping my size. This was especially true of once we got 4:1 bp. AT some point, It finally just scared me. I'm not a million dollar trader. I will be though, someday. But I don't need to do it in one year. I found that having about 2 weeks of consecutive 5 figure days (some up, some down) that the size had finally caught up with me. I swung my account in a 40k range, and at the end of 2 weeks I was up a measly 5k or so. I realized that it was time to drop it down again. I'm quite happy with just 2-3k a day, as long as i can do it every day. That doesn't scare me though from occasionally taking serious size. I'm sitting over the weekend with 57k shares of some position I've been chomping on since the close on thursday. Most of the time though I just trade much smaller.
I have found that keeping my account at 60k, and sweeping it down every time it gets to 80k, that I can keep my account swings much smaller. I use my winnings to "invest" in ideas I have.