I was rather taken by this which I stumbled across the other day:
A curmudgeon often has a black sense of humor. They don't just complain about things, they do it with flair, style, panache, satire, and a sardonic view of life! That's what makes them memorable. They also, deep down (very deep down), believe that by saying something about it, life will change. Saying even more about it will hopefully make life change faster and sooner.(That’s meant to be green ink, in case you were wondering)
All it takes to change the world, making life the way it used to be, is for people to pay attention. Instead of running around like a bunch of chickens with no heads, people — particularly young people — should spend a few hours listening to curmudgeons. Then they'd know what the real world is all about.
Your average grump and grouch are just complainers. They moan and groan about how things are going wrong, they don't like this and they don't like that. But a curmudgeon has a world outlook. They see that entire societies and civilizations are going to Hell in a hand-basket!
A grouch understands that things are pretty bad, but they're probably getting better. A curmudgeon knows that things may be getting better, but that everything is about to get worse.