It's in the blood! Once you understood how it works, you can ballpark with the 4/2 rule, but it is only really necessary in cashgames if you are planning to play 2 or 3 lifetimes. In tournament it is more important to ask yourself whether you want to go home or if you want to stay in the tournament. Or what does the call / fold do to my ICM.
In general you see your cards, the board, and the behaviour of your opponent. You have an open ended straight-flush draw? Bet your house and sleep under the bridge! You have good chances, but there's a chance the pokersite gives you the (probably) monster just and only to bet your house, because they like to see ppl sleeping under the bridge.
Many times your opponent has two cards of the same suit and ooops, all the odds and outs are not really mathematics. They are only a way to explain how poker works. In general you should not bet on cards that are about to come, rather on hands you've already made.
9 ppl at the table 7folds: 14 cards are out of the game, that's around 25% of all reamining cards, but in all calculations/expectations they assume the cards we need are still in the deck???? Well, let's ask Adam Riese.... He is laughing like crazy!!!:icon_flow