Your attitude is like a box of crayons that color your world. Constantly color your picture gray, and your picture will always be bleak. Try adding some bright colors to the picture by including humor, and your picture begins to lighten up.
When times get tough, at some point, people instinctively know they need to lighten up in order to get through it.
A little perspective, like a little humor, goes a long way.
You may not be able to change a situation, but with humor you can change your attitude about it.
Laughter can help relieve tension in even the heaviest of matters.