Our brains are not hardwired for optimism or pessimism, so you can learn to accentuate the positive. Here’s how:

• Learn to meditate. An eight-week program of daily mindfulness meditation — trying to stay in the moment without distracting thoughts — increased activation of the left prefrontal lobe in study subjects.
• Think in threes. Approximately three positive moments are needed to counteract one negative one, according to Fredrickson. So volunteer, listen to music you like, or pet a puppy.
• Write it down. Martin Seligman, the psychologist who authored the book Authentic Happiness, suggests you create a journal. Every night, write down three good things that happened that day — and include an explanation for why each happened.