Writing down three things you're grateful for at the end of each day, and why they happened, leads to long term increases in happiness and decreases in depressive symptoms, according to a 2005 study from Martin Seligman, director of the Positive Psychology Center at the University of Pennsylvania.

It doesn't matter how large or small each thing is -- just write them down, in a notebook or your Notes app or wherever. 

The point is to train your mind to orient itself to the parts of your life that are good, instead of directing your attention to things that are stressful or irritating.

You may have already tried all those mindfulness apps. But exercises like meditation that teach your brain to focus on the present instead of the past or future can increase feelings of self-acceptance.

"The idea is to be present -- don't judge your emotions, but recognize them," says Elizabeth Dunn, a psychology professor at the University of British Columbia.

(Another caveat: If you have PTSD, proceed with caution or check with your doctor first, as mindfulness exercises may be triggering, experts say, because they can unearth trauma.) 

Particularly in the West, people have adopted a propensity for self-criticism as a cultural value, and tend to self-punish when dealing with setbacks and failures, she says. But excessive self-criticism gets in the way of achieving your goals. 

There are three parts to practicing self-compassion, and they draw on some of the other exercises on this list: Be present in the moment rather than dwelling on the past or looking anxiously to the future.

Understand that setbacks are part of being human, and all people experience them. Cultivate a warm, supportive inner voice rather than a hostile, self-critical one.