OK, question in follow-up.
If the flop is all undercards, are you going to fold? Doubt it, its -EV to do if you do.
We can SUSPECT we are beat sometimes but still have to grab our ankles and call - that too is just part of the game and something all beginners must learn as well.
What y'all are saying here is that there are times you're 90%+ certain that you're beaten, but you'll call anyway, right?

How do you differentiate between these hands and those where you say "you know, I just don't belong in this pot any more..."?