I once did fall into FOMO trap and lesson was learnt in a hard way. Currently, the price is gaining for some reasons. I'm thinking about selling some especially when things settle because I doubt that it'll be FOMO. Even then, it's still difficult to decide at what price to sell.
That's it, the best reference when altcoins are surging or gained massive pump is when there's significant progress of their crypto projects or products in line with their road maps.
most of the new altcoins today are having their own crypto projects so if some altcoins are pumping with no reasons it might be pumped intentionally by some Pump&Dump groups and people lose their investments when they invest out of FOMO.