I totally endorse reading Trading in the Zone by Mark Douglas - best book there is on the psychology of trading, plus I'd add Van K. Tharp's Trade Your Way to Financial Freedom.
I've never seen a financial comparison of how successful individual day traders are but I suspect a good ST trader with a turnover of anything from intra-day to several weeks (i.e. letting profits run) can make as much profit, if not more, with less stress. Also, as Mark Douglas emphasises, it does not matter what system one uses to make money in a market, the system is only as good as the operator's commitment to (1) create a personalised trading plan; (2) test and measure that plan to refine it; and (3) rigorously stick to the plan so it can be tested.