http://en.wikipedia.org/wiki/Kierkegaard

Kierkegaard was the first existential philosopher, and his ideas are a foundation for existential psychology. I hope that it's okay to refer to him. He was also a theologian, so this, like most concepts in philosophy, involve spirituality and belief (or lack thereof). The whole point, though, is that you have to find what you believe in, not just adopt someone else's beliefs.