Happiness is when the inner self is in high spirits due to some satisfaction that he has yearned for quite some time.
Happiness is bliss, contentment and peace of mind for some.
Happiness leads to a moment of enjoyment, an euphoria which leads man to ecstasy even without any drugs.
Man is a dreamer and when his dreams, ambitions, goals, or something nice triggers for him, his heart tends to melt and secrete those hormones that leads to a smile as his inner self rejuvenates over it.
Happiness is an expression of love. A love and an yearning from within for someone or for oneself.
Promising to be happy for just that day can do wonders.
Try it, and feel the gush of happiness flow through you for that selective day and you will be amazed at how powerful your thoughts can be!