I would say that the right time to sell is different for every user, there is no "general right time".'
It depends on many factors, like at what price has one bought Bitcoin or earned it, what are your plans and trading or saving goals, do you need money etc. So basicly everyone should make the decision on its' own but if you ask me the Bitcoin price has many room for further growth so there is no reason for selling unless you need/want to.