Great post, with some excellent points. They way I see it ...

When things are down, realize that "All this will pass."
When things don't pass soon enough, realize that "Adversity builds character."
When things continue to be less than ideal, understand that "Someone else probably needs my help or support." Provide the help and support.
When things turn around and everything starts to look rosy, realize that "Life is good." Then strive to make it better, for both you and others.
Repeat as necessary.