If  we couldn't laugh we would all go insane                                                                                                                                                                                  - Robert Frost

Meaning: Laughing is what? Don't over think its just a small thing which make as happy. It's something which is one among the most required things in our life. If a person couldn't laugh he will certainly feel irritated,confused and mad. 

And actually for me there was no need to explain the quote, the quote says it all.