Life is, in the end, like a tragedy - many of us are admirable people, but have our own flaws that undo us. By the time we are done with life, events unfold in a way that lead us to our doom. Death is an inescapable and unfortunate part of life - much like tragic characters, we move inexorably toward it, often without understanding exactly what we are doing.
My grandfather was an amazing man; he was a war hero in World War II, a dedicated family man, and an incredible role model. However, his one vice was smoking, which inevitably led him to his fate; at the age of 63, he developed lung cancer. Within a year, he was gone, and a family was left without its patriarch. Tragedies take the one significant flaw in a character and use that to destroy them, no matter how sympathetic they may be.
My best friend in high school helped me throughout my formative years in many ways; we played together, he taught me how to make friends, and much more. However, there was another group of friends who were more popular at our school, and he wanted to be part of that in order to have more power at school. To that end, he cut me off, severing nearly a decade of friendship for a trifling stint at popularity. As a result, he lost me as a friend forever, and that group of friends ditched him quickly when they got tired of him. He was a tragic character; his search for belonging and popularity left him with no friends.
In conclusion, the inherently finite nature of life often makes it a tragedy. Humanity and our individual personalities are not without flaws, and those flaws often are our undoing. No matter what happens, or how good we are, people experience major setbacks, often because of the one thing that is wrong with them or that they overlook. To that end, life is much more a tragedy than a comedy.