The essence of life lies in how to live it with happiness. If you define happiness, it is just the state of mind and nothing else. Happiness or misery depends on our reaction to circumstances, not on circumstances itself.
Life is what we make it: A basket of surprises with little anticipations and full of opportunities. Remember, happiness lies in the moments of present, memories of past and dreams of future. So lead a life full of moments, filled with memories and engrossed with dreams.