You might heard of 10000 hours rule by Malcolm Gladwell, which is to invest 10000 hours to master something. But how do you know which domain you would like to spend 10000 hours in the beginning? Introducing my 10 hours theory. Actually, it's 10,100,1000,10000 hours theory. By investing 10 hours at the very beginning, you can make sure the rest of 9990 hours you will spend is a good investment.