Interesting theory, but it presumes that idealism or pessimism are root states of being that have no cause themselves. Idealism does not just spawn out of nowhere, it typically, I think, is rooted itself in a belief in something or someone else.
It is the object of ones trust or comfort that makes one an idealist. For the Christian that source of idealism (which in the Christian faith is really just a component of faith) is a knowledge of the character and nature of God. For other idealists their positive idea of the world and how things will turn out stems from other things such as security in finances, a belief in the invincibility of youth, trust that government will take care of you, or a whole host of other factors that cause them to not we worried or look at things negatively.
Our ideas of God ultimately shape whether we will trust Him or not. It is when we let temporal factors effect us and less Jesus that we are swayed towards either an irrational and unsecure idealism which can crumble before us, or a pessimism that keeps us gripped with fear and caution day in and day out.