[kstenerud]

The sustained assertion of your mental will over the baser impulses of your body, usually in anticipation of a better long term result.

This can be something as simple as resisting a temptation (saving money instead of splurging), to something more complex like a routine activity that your body tries to reject (such as exercise or keeping the house tidy). The most difficult is discipline over your own thoughts (which tend to change with your mood and emotions), or remaining focused on a distant goal when daily progress is difficult to measure.

[Dewie3]

Willpower is great for when you have no belief in your own instincts or smarter approaches to getting what you want, which for some people is always. It's a great tool for smashing square pegs (with sufficient force) into whatever shape of hole you are faced with.

> The most difficult is discipline over your own thoughts (which tend to change with your mood and emotions),

I think thoughts come before and inspire moods and emotions, more than vice versa.

It's hard to maintain discipline over your own thoughts because it's like trying to redirect the Amazon river with a teaspoon. It tends to be more effective to try to gently steer it in a certain direction, or try to quiet it altogether (meditation).