Learning how to smile. I would spend time in front of the mirror practicing my smile for different situations.

During interviews I would force myself to smile. It helped get rid of some nervousness. When I get stuck on a problem I would smile stupidly and usually the interviewer would help me out.

When I feel like conversations are getting heated I would take a step back and smile, it helps me direct the conversion to a more positive place.

Sometimes when stuff happens outside my control and life just sucks I'll force myself to smile and handle things to the best of my ability