If you want to sell the tokens, then sell them right after entry into the exchanges. Further the price of them only falls. Seldom what project manages to hold or even to raise the price of the token.
Your statement is simply not true. Many tokens has perform well after hitting the market. I am sorry, that you did not have any successful tokens. The most important is how is the project doing, is it moving forward or it is going down. If I decide that the project is promising, I will hold as long as I believe that I see progress.
Of the many tokens that exist, there are more who fail when compared to those who managed to advance further and even enter the top 100 in coinmarketcap. It is difficult to find tokens that continue to go further, but if we continue to learn from mistakes, then you will also find the best.