1. Over trading 2. Not patient enough to wait for your trade 3. Trading scared / Missing entry / Selling too soon 4. Can't let winners run 5. Can't cut losers
My automated strategies P/F are all in the 1.3-1.7 range, I don't have many of them (only 3 live at this time), and 2 of them trade ultra-low frequency (< 5 trades / week), which essentially means drawdowns can last for months. The last once has better frequency (~ 2 / day), but huge P&L swings, making it a roller-coaster ride. On the plus side, I am now able to run all my strategies without any interference, just a few swear words here & there. So, my main weakness is my limited edges, not the execution side.
My addiction to Angry Birds. It would be nice to have a World crises edition with Extra Volatility for the best trading experience... See below: I would just hope Wile E Coyote would not get upset for using his brand of Genus products...
I think the biggest problem for 99% of day traders is not having a winning method. The "most people aren't disciplined" answer assumes those people have a winning system to follow in the first place.