Be aware of what situations and behaviors give you pleasure. When you feel excessively sad and cannot change your attitude, make a conscious effort to take some action that might alleviate your sadness.
If you anticipate feeling sad, prepare a list of things that might make you feel better. It could be talking to a specific enthusiastic individual, running, taking a walk in a quiet area, looking at pictures of family, listening to music, or reading inspiring words.
While our attitude is a major factor in sadness, lack of positive external situations and events play an important role in how we feel.
-from Rabbi Zelig Pliskin’s Gateway to Happiness, p.180