We all have willpower but it is a limited amount. Every decision or stress will deplete the resource, so you have to save it up. You can top it up with meditation or a good nights sleep.
When we fail and think we don’t have willpower the thought that we have no willpower will defeat us before we even begin. What if you could just do a task, say no when you have no willpower, by utilising a different thought process rather than depend upon willpower will move you forward more effectively and with ease and rather than defeat.