This quote means that having a sense of humor is so important to the speaker that if he did not have it, he would have taken his own life some time ago. Humor can be a way for people to cope with difficult times, and it can make even the most challenging situations more bearable. It gives people a way to look at things differently and find something humorous or amusing. In this case, the quote suggests that the speaker values his sense of humor so much that if he didn’t have it, he would not be able to cope with life and would have ended it.