What complications come with living with fear that the future is indeterminate and life is utterly useless and complex? Why do some of us tend to question our existence while others settle for living in the present? What's so crucial about us that gives us a feeling of a void?
With a current world population of over 7 billion people, one really cannot make accurate statements about people in general. There is tremendous variation in cultural traditions, individual circumstances, and individual psychology.
Within Dante's Inferno, which exemplified medieval Catholic theology, despair was considered the worst of the seven deadly sins because it denied the possibility of salvation. Ignatius Loyola and other theologians prescribed spiritual exercises as a remedy for the "dark night of the soul." In general, within religious communities of all types there are various forms of ritual and mental practices and belief systems designed to give life goals and meaning.
For atheistic philosophical systems, including various forms of Existentialism and Utilitarianism, the quest for meaning in existence is more complex, either lying in enjoying the moment or in choosing a purpose as an act of will.
A pragmatist would argue that feelings that the future is indeterminate and that we live in a void are simply not very useful ideological constructs. In our daily lives, we need to plan for the future by doing things like getting degrees, building work experience, maintaining our credit ratings, etc. If we do not have a belief system which enables us to do these things, we will have a determinately bad future of debt and joblessness.
While formless angst is often a temporary stage in adolescent development, persistent feelings of despair or hopelessness may be signs of clinical depression and should be treated by a medical professional.