You know when it's the time to sell when the market becomes bullish for an extended period of time. When you see major cryptocurrencies with a price increase of over 2% during the day, you know that they're going to keep rising in price for a while. But when the increase is 1% or less, the effects would only be temporary as the cryptocurrency or token will quickly enter in "bearish" mode. Despite this, we can never predict with certainty what will happen with the price of a cryptocurrency due to the unpredictable nature of the market.

As a word of advice, only invest into solid projects with a proven track record of development and innovation instead of projects that are full of hype. If you do that, then you'll be on a road towards long-term financial stability. Just my thoughts