Every poker game has its fish. In poker terminology a fish is a sucker, and one might go so far as to say that the weakest player at any poker table is the fish. This would mean that at one time or another every poker player has been another poker player's fish!
Poker players tend to be incredibly arrogant or at least highly self-confident, especially when it comes to their ability at cards. For that reason alone it is mentally healthy to remind oneself that being a fish is a rite of passage we all have to swim through, and that no one is a shark all of the time.
Online poker rooms that are part of larger gambling websites that also offer casino and sportsbook components tend to have a higher proportion of fish or weak players. Look for those rooms and cash in big by hooking some fish of your own on the river!