20% profit is very good, but once you start playing every day/week/month always targeting 20% profit, at some point it won't work anymore. On long term it won't work. Like you say, 20% daily, in 5 days you double your money, but what is the difference between this gambler and the gambler who tries to double his money in one day?
The difference is that the second gambler will probably lose his money 5x faster.
(But all of them will lose money anyway).
A gambler who tries to double his money in one day? That gambler may lose everything his money by chasing to win for money, maybe out of control in gambling is have a bad effect on it. Don't let gamblings control you, you should be learned how to control your emotion in gambling then stop if 30% of your fund had lost and come back tomorrow.