Spending money and using health items in any game, with the notable exception of Dark Souls.
There's always a moment in the game where I'll see something I want to buy and think, "No. Save the money. Something good will come along later." Then it doesn't and I'm stuck with a Steel Sword while my enemy is caving my skull in with his +8 Axe of Awesomeness. Of course, on the rare occasions where I do spend money to buy better equipment, something better comes along that I can't buy because I spent my money on the last thing! It drives me crazy!
Health items are weird. I always manage to get out of a situation without using them, thinking I'll need them later. Then, lo and behold, I end up having about 40 of them, making the boss fight too easy because I can heal after every single attack. The only reason I'd need that many is if I'd go after the super difficult, optional boss battles, who has an attack that can kill me in one hit so they're useless anyway!
The only reason Dark Souls is different is because farming for souls is second nature to me now, and I know I can get to a bonfire to refill my health items. Go figure.