The point is not that this world is too sad to love or too glad not to love; the point is that when you do love a thing, its gladness is a reason for loving it, and its sadness a reason for loving it more.
Thoughts are no more than electrical surges in the brain. Sexual arousal is no more than a flow of chemicals to certain nerve endings. Sadness is no more than a bit of acid transfixed in the cerebellum. In short, the body is a machine, subject to the same laws of electricity and mechanics as an electron or clock.
The boy was lying, fast asleep, on a rude bed upon the floor; so pale with anxiety, and sadness, and the closeness of his prison, that he looked like death; not death as it shews in shroud and coffin, but in the guise it wears when life has just departed; when a young and gentle spirit has, but an instant, fled to Heaven: and the gross air of the world has not had time to breathe upon the changing dust it hallowed.
When sadness comes, just sit by the side and look at it and say, "I am the watcher, I am not sadness," and see the difference. Immediately you have cut the very root of sadness. It is no more nourished. It will die of starvation. We feed these emotions by being identified with them.
But it is a melancholy of mine own, compounded of many simples, extracted from many objects, and indeed the sundry contemplation of my travels, which, by often rumination, wraps me in the most humorous sadness.
Thousands of lives were suddenly ended by evil, despicable acts of terror. The pictures of airplanes flying into buildings, fires burning, huge structures collapsing, have filled us with disbelief, terrible sadness and a quiet, unyielding anger.
Christianity satisfies suddenly and perfectly man's ancestral instinct for being the right way up; satisfies it supremely in this, that by its creed Joy becomes something gigantic, and Sadness something special and small.
I think all tragedies are best told with some humor. You have to relieve the darkness to let the reader get through it. Also, that life has happiness and sadness mixed together. If you told a story that was all darkness, it wouldn't be real.