This is a note from my reading – The Life Book, Nina Grunfeld. p.164.
Happiness is when you feel pleasure, contentment, satisfaction or joy. Researchers have found that 50 per cent of happiness is genetic, 10-15 per cent is due to measurable life circumstances, such as money, marital status, income, health etc. The remaining 35-40 per cent is to do with the actions individuals take to become happier.