Fools who wear their hearts proudly on their sleeves, who cannot control their emotions, who wallow in sad memories and allow themselves to be provoked this easily - weak people, in other words.Severus Snape in Harry Potter and the Order of the Phoenix
In other words, you don't want to be serious
It takes two to be serious.
There are some things so serious you have to laugh at them.Niels Bohr
I think you should take your job seriously, but not yourself - that is the best combination.Judi Dench
Take your work seriously, but never yourself.Margot Fonteyn