Futures are a contract that match up a buyer and seller at a specific price, with the buyer agreeing to pay that price for the asset when the contract expires in the future. The seller is agreeing to deliver the asset, like oil for example, to the buyer when the contract expires. Day traders are never required to deliver or pay for the actual asset, because all positions are opened and closed within the day (no open obligations). Profits are losses are based on the prices the contract is opened and closed at.
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.