Psychologist and best-selling author Shawn Achor has made a career studying the science of happiness. "Scientifically, happiness is a choice," Achor says. He explains that research has shown you can rewire your brain to make yourself happy by practising simple happiness exercises. Achor says in just 21 days, the exercises can transform a pessimist into an optimist. And within 30 days, those habits change the neuropathways of our brains and turn us into lifelong optimists. These six daily happiness exercises are proven to make anyone, from a 4-year old to an 84-year old, happy, or simply happier, Achor says: 1. Gratitude Exercises. Write down three things you're grateful for that occurred over the last 24 hours. They don't have to be profound. 2. The Doubler. Take one positive experience from the past 24 hours and spend two minutes writing down every detail about that experience. As you remember it, your brain labels it as meaningful and deepens the imprint. 3. The Fun Fifteen. Do 15 minutes of a fun cardio activity, like gardening or walking the dog, every day. The effects of daily cardio can be as effective as taking an antidepressant. 4. Meditation. Every day take two minutes to stop whatever you're doing and concentrate on breathing. 5. Conscious act of kindness. At the start of every day, send a short email or text praising someone you know. 6. Deepen Social Connections. Spend time with family and friends.