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I usually have 30-60% of my funds in cash, preferably in Euros (dollar isn't programmed to rise, ask the FED).
Frequent ins and outs are better than relying on a coin to do what one expects, but it's f course also more of a job ;)
But why would someone ride out a dip of days or weeks if they can make a deal of it ? To be able to say "I'm not a weak hand, I'm a hodler ?" I'm not sure if such people exist, there will be many who are simply indecisive and therefore prefer to ride it out, which is understandable if you're unprepared.