If the person seems never happy and beyond the norm of mellow the term depressed seems possible Are the eyes either downcast or seemingly in a distant. discontented
A person who is never happy can be called a malcontent.
antagonist? maybe, not sure
No. The word person is a noun. So are the words that mean a specific type of person.
Bummer, downer, drag, pessimist
You will never become the "smartest " person on earth, but have to be happy with who you are and the things you can accomplish.
A smiling manniquin. Either that or a Mental Emotion.
Never, if everyone involved is happy with the situation.
Im happy person
The word "happy" is an adjective, and "very" is an adverb that modifies happy.
Sadist
To contemplate the past; usually happy events in a person's life.
As a person of few scruples he was more than happy to take the credit for another person's work.