I myself also still learn a lot about trading system. I think selling when coins are high prices. And buy when the price of coins is low. So the profit earned can be set aside. And the initial capital can be to re-buy coins when the price is low. And so on, if I think.
Buy low and sell high. It is the best strategy as a trader and if you want to see your real profit, invest in bitcoin in a dollar then the profit of your investment use it to buy again and your capital just keep it. You must use your profit to buy again in bitcoin and set the desire value of the bitcoin when you sell it. Your money will grow if you holding your bitcoin and sell it in a high price.