Ever wonder why sometimes you cannot avoid giving into temptations? Or why shops always put the candy/chocolate near the checkout?
Willpower is like a mental muscle. It tires and it grows. In simple terms, willpower depletes with use and gets stronger the more you use it.
Ergo, if you are tempted multiple times throughout the day, you will most likely give in eventually. More importantly, if you spent the day resisting temptations and then come to another, you’ll have a hard time resisting it.
Let’s say you spend the first half of the day at home and there is leftover cake that you wanted to save for later. But you really want to eat it now. Therefore, every time you walk past, you’ll be depleting some willpower by resisting the temptation. Now, say you go to work for the other half of the day (after having successfully not eaten the cake) and your boss is away, leaving you alone. It is Friday and it’s half an hour before your normal leaving time. No one will notice that you’re gone. Because of your depleted willpower, you give in and go home. However, if the cake hadn’t been at your house, you would probably have been able to resist the temptation to leave work early.
Now, more interestingly, making decisions also drains willpower. Or rather, excluding options (by choosing others) take willpower because people don’t like losing options. Regardless, this affects how people make decisions. Like, say, the supermarket candy. They put it at the checkout, after people made a lot of decisions, thereby lowering their ability to resist taking a chocolate.