Sometimes this is very obvious in people, as they come across very difficult, angry or maybe the complete opposite in being depressed or negative.
I personally have found myself in these places but the one thing that has kept me going is a belief in God.
Everyday I place my day in the hands of God, and spend the day communicating with God and following the example of Jesus.
I also feel serving others helps with the walk we are on. Talking our mind off ourselves and our unhappiness, and finding fulfillment in helping out.