A person will clearly understand the reason for the profit, whether it had happened out of luck or as a result of the analysis made. In all means users need to have patience handling the situations. Based on what the OP have achieved is great, because with $100 as capital making another $80 as profit in two days time is really big. One should not expect the consistency in the earning, because the volatility range varies and the same could cause difference in the earning. When it comes to trading, one should not allow the capital to go down in value.
This success story doesn't mean that anyone who invest in Bitcoin will get success. We have heard many stories where people invest in Bitcoin after reading such success stories and were not successful. Bitcoin is not about investing 100$ and getting profit after a week or month. It's a volatile and can move in both directions.
If a person has good knowledge about Bitcoin then he can easily earn a lot of money from Bitcoin and change his life style in a short period of time.
I don't think that's true. You may get profit occasionally if you are investing for short term but real benefit comes only if you are investing for long term. It doesn't matter how much you invest, as long as you are investing for long term you will get good ROI.