die
Explanation
The Joke
A man has an existential thought: "I'm going to die one day." He then chides himself, thinking he should try to think more positive things. In the third panel, his idea of "positive thinking" is: "EVERYONE will die one day." The final panel shows him walking away whistling happily, clearly cheered up by this reframing.
The humor lies in the character's deeply flawed understanding of what "thinking positive" means. Instead of pivoting to something genuinely uplifting -- like gratitude for being alive, or the beauty of the world -- he simply expands the scope of his morbid thought to include all of humanity. The universality of death is, to him, a comforting thought rather than an even more depressing one.
The Humor
This comic plays on the psychological concept of "misery loves company" taken to its logical extreme. There is a real human tendency to feel better about our own suffering when we learn that others share it -- but extending "I will die" to "everyone will die" is a darkly comedic version of that coping mechanism. The whistling in the final panel seals the joke: the character is genuinely, blissfully satisfied with his reframe, oblivious to how morbid it still is. It is a quintessential SMBC take on how humans process existential dread -- not by overcoming it, but by finding creative ways to be comfortable with it.