Most successful investment strategy is buy when everyone is selling and sell when everyone is buying which can be long term or short term but definitely it is the most successful one.
I also apply the method like you, but to apply this method we must be patient and also good at seeing the right moment to buy or sell the cryptocurrency that we invest, if these two things are not with us then don't expect too much big profit, because there are so many investors who lose when their predictions are not right