There is not really a universal rule to use.
Are you trading based on fundamental or technical analysis?
The fundamentals are always different so no situation is the same.The answer depends on "why" you bought the cryptocurrency to begin with. For example when you go long and a certain catalysts haven't played out yet. Is it worth closing for loss when original thesis is still pending? I don't think so.
With technical analysis it's often more straight forward. When you are trading Elliott waves and you hit a certain fib realising the trade won't work out. Then you simply cut your loss. Just put your stop loss order around the Fibonacci targets that you are working with.
