I think the best time is when your asset is 10-30% more than the purchase price. Of course your needs can be matched with your expected price. However, if you do not want to lose, it is better to go out first. Moreover, if the market conditions are good, you can wait a little if you want, and if not, it is ironic to come out as soon as possible.
I think 10 to 30% profit is good enough to sell your coin, don't greed just sell when you have that much profit. One other strategy can be that set a target price and sell as soon as you see that price. If you keep on waiting for more and more profit then chances are that you may end up in loss.