It is necessary to sell the coin when its price rise to have the maximum profit from investment.
But when market falls it necessary to buy coins.
But not all coins will be able to survive during fall of the market. That is why it is important to evaluate the future potential of the coin.
That's true, but for those who have been familiar with coins in the past will always look at coins with potential like those in the top 10 cryptocurrencies today.
Because it will also save them more time if they have to evaluate repeatedly on the same coin.