What are the simplest things one can do to make oneself happier?

by Fuyang

Answer by Brad Einarsen on Quora:

When I was in a dark period I instituted a simple rule that changed my life.

Rule: When I arrive home from work, the very first thing I tell my wife is the best thing that happened that day.

No exceptions. No complaining. Just the best thing that day, even if it was just a good cup of coffee. This had the effect of starting our evening off on a positive note and it changed our relationship.

What are the simplest things one can do to make oneself happier?