Better depressed and safe, than happy and sorry.
"Researchers argue humans did not evolve to be consistently happy but primarily survive and reproduce. Evolution, they say, placed an advantage on depression, preventing humans from engaging in risky or hopeless situations."
Whilst I agree we have evolved to feel dissatisfaction, I feel it is wrong think we have not also evolved to feel gratified; which arguably involves the act of being happy.
We even plan in advance events to make us happy which is a highly complex interaction between emotion and executive functions.