I mean if we could always buy at the perfect timing and sell at the perfect timing then we would make a lot of more money with trading than investing. So every time the prices drop we sell, and will rebuy once the prices rise again. Unfortunately we can't predict the perfect time to buy or sell very easily, there are a lot of factors to consider. If we buy and sell at the wrong time we will make a loss. Which is why investing seems to be more profitable in the long run.
Indeed! The tough part of trading is the timing we can't accurately predict the market now even we already done doing our good research.
There are still chances that the price will go not according to your plans, you need to have long patience and and a good nerve to handle the risk that it takes when working with this kind of business, unlike with investing if you have set targets then you don't need to worry just hold and wait.