Day trading poses a number of hurdles. Mainly, each trading day is slightly different. Traders need a method that works in nearly all market conditions. That doesn't mean a day trader will win every day. On the contrary, even with a great method, there still may be several losing days a month. Winning every trade or every day isn't important, it is winning over the course of each week and month that matters.
Assess how much capital you're willing to risk on each trade. Many successful day traders risk less than 1% to 2% of their account per trade. If you have a $40,000 trading account and are willing to risk 0.5% of your capital on each trade, your maximum loss per trade is $200 (0.005 x $40,000). Set aside a surplus amount of funds you can trade with and you're prepared to lose. Remember, it may or may not happen.