If you are underwater too long, you know exactly what you want: air. If you are very hungry, to the point of it being a health issue, you know what you want: fo

If you are underwater too long, you know exactly what you want: air. If you are very hungry, to the point of it being a health issue, you know what you want: food. If you are desperately poor, to the point that you have to worry about getting food and shelter, you know what you want: income/money. If you are desperately lonely, you know what you want: companionship. Etc. At some point, your basic needs are met. If you don't know what you want, it's because there is no longer one overriding need that needs to be met. Thus, the difference between getting one thing vs. another is not as large. So, one will have to use some willpower/mental tricks/etc. to stay on task, because there is not one overriding need. Control circuits have to do something similar when, for example, they are very near the setpoint temperature, otherwise it will cycle back between heating and cooling way too often. If you don't know what you want, you have most of what you want, so one will simply have to pick up an aversion to switching objectives too often, just like that thermostat's control circuit.