Acceptance.
Some times in life people are unhappy just because they have a hard time accepting their current state of life.Where as life can be very happy just accepting that this is what my life is,I may not be meant to live like this ,but the truth is ,now I can not change it anymore.This little realization can bring great happiness .I am not asking to become complacent but realization of your ground is some times very self soothing.