Don't fear failing

Almost all of students have low self-esteem at high school where I work.
So they always talk about "I will not do it, because I can not do it."
They give up something before they try to do it. They have ever had few successful experience.
They are afraid of failing. If they would not try anything, their life will become nothing.
At that time I take part of a listener before encouraging them.
I want to know what causes. I guess what he only lost willingness or she has a bigger problem than this class or they are just lazy....
My handling will change depend on that states.
At any rate, I want them to try anything and have many experiences.