[Kurn]

The real key decision point in HE is the turn. By that time, you should have a fairly clear idea of the range of hands your opponent is betting. There are several situations were it's correct to call the turn and fold the river (busted draws, for example) or bet the turn, fold the river (2-suited cards on the flop, you're in position, weak-tight or loose passive opponent has been check-calling all the way, now bets when the third flush card hits). However, when the pot reached the 10 BB range and you have something, it's not out the realm of possibility that your opponent is bluffing 10% of the time, or that the board is, say Q-9-5-2-2r your opponent has been betting JTs all the way or 88 and your T9s that you got in cheap with on the button in a multiway pot is the best hand.

This is absolutely true at higher levels as well. Now, if the opponent is one who you're sure would never lead on every street without TP, then go ahead and fold. Fold too much on the river and it's like you're wearing a sign that says "take shots at me". It's only one bet. If you're winning more than 75% of the time you go to showdown, you're probably folding too much on the end. If you're making good decisions leading up to the river, lowering your win rate at showdown from 80% to 67% should increase your win rate.

Say you're winning 80%, so 80/100 hands you call at the river. Now you decide to fold half as often, so you call at the river 150 times instead of 100, but you win 60%, so that 90/150. That's 50 extra bets invested, and let's say the 10 pots you win out of those 50 average only 7 BB each, that's another +20 BB over the same number of hands. (additional edit) Just like in baseball, where the difference between a .250 hitter and a .300 is one hit per week, the difference between a break-even poker player and a winning poker player, is less than one big pot per session.

I don't think this estimate is out of control. 10% bluffs and 10% the lower end of the range of hands the opponent would value bet.

Edit: Don't read Cardplayer for strategy advice. Cardplayer is in the entertainment business.