Life is a gamble. If you sell immediately you make a sure gain, as many coins lose value. But you lose the chance to make a big profit, if the currency explodes.
Losing a big chance to profit is what I fear the most which is why I sometimes regret selling the tokens I got. But somehow keeping the BTC I got from it made me feel at ease still. Its the BTC that's most important for some people that includes me. There are just coins that are hard to dump like EIDOO and waves that I kept for so long already.