Psychologically it's our desire ( large sense), that gives us the force to exist.
Without this desire, we wouldn't want to live.
A psychoanalyst told me once: a child who doesn't have this desire, refuse to live and so, he/her lets he/herself to die.. They see this type of cases in their offices.
Also we know that people who have depression have a deep lack of this desire, that is why they want to suicide.
Children too, can to have depression by the way.
For the end, I would say that this desire intervenes in anything we want to do in our personal lives: make choices / decisions ( important or not), our sexuality, want to do / make things, etc. Etc .. ANYTHING!
◘ Note: Depression mustn't be confused with a simple depressed state, which is momentary contrary to depression.