No matter wherever you do, what you do for work, follow your heart, trust your own instinct, sometimes do what your impluse tell you do - just like Louise-give a note to the man on the street, which she writes down her happiness she has.
In the opposite way, Louise's sister Martine seems have a perfect life but she hates herself and life. We all like her sometimes in our life. So do something to change it if you are unhappy with yourself.
