When media talks often about the dump and publish articles, then that is the RIGHT TIME TO EXIT.
News, rumours, speculations could have a big impact and can affect the price of altcoins. They concide the price movements resulting in pump and dump.
Believe me, I did that and it really works. Prevents deficits and prevents loss of investment.
Most of the time this works, though I must say that it isn't applicable most of the time as exiting a certain position is entirely subjective, as to what a user above stated.
Usually the best time to exit is when everyone is rejoicing and are highly optimistic that the coin will continue to rise even with a recent unsustainable growth. It's okay to lose a couple % of gains rather to lose it due to being greedy. When already at a loss, mental fortitude and controlling one's emotions is really a must if you want to breakeven or profit a little. It's okay to be bag holders rather than throw those bags only for them to appreciate later. The thing is, investing in crypto is a roller coaster, and you must know when to exit and enter; news are massive sources of signals since traders use them for their situation.