That begs the question, how do you do it then? Here are the steps to success as a day trader as I see it.
1. Success at trading. Don't try to day trade until you've proven to yourself that you can trade successfully at a much slower pace.
2. Sufficient capital. If your trading account isn't in the high five figures, you shouldn't day trade (if that's going to be your only source of income).
3. A winning system. Day trading is harder than any other kind of trading that I know of. You really need to make sure your system will hold up. A system that works in a slower time frame will not necessarily work for day trading. Make sure you're system has a positive expectation.
4. Practice. Practice makes perfect. Yes, it's a tired old phrase, but it's true.
5. Patience. The market will try to destroy you as a new day trader. Have patience. Hang tough. You will make it, provided the previous four items are in order.