For those who may not know, Existentialism can be briefly described as: stressing that people are entirely free and therefore responsible for what they make of themselves. With this responsibility comes a profound sense of anguish or dread.

This sums up what you - and many of us with mental illness - ponder. It is my belief that thinking existentially is about looking for a sense of purpose. Lacking that sense of purpose is one of the hallmarks of Depression. It is linked to hopelessness and worthlessness.

Similarly, one of those things that breaks the Depression is a sudden realization of a sense of purpose - and an "I think therefore I am" moment.