Most negative conditions in life, both psychological and external, can be traced back to one underlying cause:
A lack of self-esteem.
Whole sectors of the modern economy rely on this lack and play off the powerful addictions and drives we seek to fulfill by the acquiring of goods that denote status and temporarily bolster pride.
Many books are written about how to acquire self-esteem, talking about it as if it were simply a set of beliefs one can acquire by proper internal manipulation.
But self-esteem is not the inevitable outcome of positive beliefs.
It is part of our rewards system, the most integral, least hedonistic part, that grants us joy and lasting confidence, not in return for mindless pleasures and dopamine triggers, but for virtuous action.
Lack of self-esteem is what you get when your behaviors and thought patterns do not live up to your unconscious standards of the proper and good.
Many people, in an attempt to escape from their own standards, drop those standards and thus gain the illusion of self-esteem. This is a difficult hole to come out of because once you reject your own standards and accept the improper behavior, you lose sight of what was meant to guide the course of your life.
This is why low self-esteem leads to deep bouts of hopelessness and bottomless depression. Because if you lose sight of those standards, that higher guiding force within your psyche, the future does indeed become a dark place.
It is also why to have high self-esteem is to be largely optimistic, because if you submit to your own standards, your life will proceed as is best for your capabilities and desires. A positive projection of the future will be appropriate to your conduct because your conduct will align with your goals.
Self-esteem is directly correlated with the size of the divide between you and your goals. The farther away you are from that conduct which would eventually accomplish your goals, the lower your self-esteem will be.
Self-esteem is a reward, not a treasure to dig up out of your psyche or something to be granted via the acquisition of high-status objects and environments.