From a psychological point of view, discipline belongs to the executive functions and arises mainly in the prefrontal structures of the brain, especially in the prefrontal cortex. This part of the brain also has other tasks, for example, it processes feelings from the emotional part of the brain and decides whether to react to them or not, i.e. emotion regulation takes place in this part of the brain. So when the brain is busy processing feelings like fear, shame, or anger, it has no more room for discipline. So if you’ve had a busy day because you had to take care of young children, for example, you’re usually pretty exhausted because you then have to expend energy not only on your own emotion regulation, but also on the children’s. When the maximum capacity of the executive part of the brain is reached, the brain switches to autopilot, i.e. the brain seeks short-term gratification rather than long-term goals. While it is not impossible to still have enough discipline in this state to then choose the option that will do good in the long run, most people then tend to give in to convenience. In this case, willpower is lacking not because you are weak, but because you have probably put yourself through too much and your brain does not have enough capacity to motivate itself. So the solution is not to put yourself under even more pressure and to overcome with all your might, but simply to relieve the stress.