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 (0.5% * $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.