In my opinion it's important to have a little bit of both, it takes a lot of willpower when you don't have a lot of self-esteem.
I think they are related. One is a root of the other.
Both coz both are different aspect of life.
I think the two kind of go hand in hand. You need one to have the other.
I think strong will power automatically gives you a strong sense of esteem.
While personal strengths vary, if you find yourself as an adult lacking both, it is easier to develop will power than to develop self-esteem.
If you lack self esteem, you already have a low opinion of yourself---which makes it harder to value yourself appropriately.
I am with the majority on this. They both go hand in hand.