We won't know when the coins we are holding will reach all-time highs and sell, what we can do is sell close to that ATH, as long as you've made a profit. Before investing in coins you should have a specific plan, at what price to buy and at what price to sell. The important thing is to make a profit and stay true to your goals, not necessarily to sell at the highest level. Although everyone wants to sell at that price, it is very difficult. Do not for just a little profit that you will pay the opposite price.