Why is your grandpa so grumpy?

One of the reasons old people are so grumpy is because with all their age and wisdom, young ones don't listen to them. They feel upset and disrespected for that. Also their bodies and minds don't work the way it did when they were younger and that is also a cause of irritation. They have also seen so much of unnecessary tragedy in their lives which makes them upset. And the final reason is that they can get away with it.