If you have recently lost a loved one, then it's okay to not choose happiness for awhile. Perhaps this doesn't cause us adequate suffering. If we should choose happiness, practice feeling happy, letting go of our daily complaints to anyone who will listen to us, berating God, and all the other myriad activities we indulge in to remind ourselves to be miserable, life will certainly begin to improve. This is a metaphysical truism. Think positively, feel happy, indulge in your creative, enthusiastic activities and you will inevitably draw more of the same into your life.
Happiness is a right and a choice.
Allow it a place in your life.