I mean, think about how unfair the world is - you can be born with a congenital defect that will kill you before you're 10 years old. Or even one. You can be born blind and deaf because your mother decided to drink like a sailor while pregnant. You can be born without limbs. You can be born with deformities so monstrous that they preclude you from living a normal life.
And that's just concerning BIRTH. What about what comes next? You can be crippled for life if your mother washes you in a dirty bath when you're a baby. You can die of starvation if you were born in a war-ravaged country. You can grow up illiterate because the schools near where you were born ran out of funding. You can be killed because a particular mosquito on a particular day happened to bite you and transmit a parasite to your blood stream. You can be killed merely because your parents happen to have been of a religious bent that wasn't your choice. You can be horrifically maimed by a simple accident that you couldn't prevent.
Life's unfair. Life's not cruel, because cruelty implies intent - and the world doesn't have intent. Humans have intent, but rocks, water, genes, wind, viruses and mosquitoes don't - they just work the way they do, according to the laws of physics and biology. The world isn't cruel, it's uncaring, unthinking, and just.....just IS. The universe JUST IS the way it is, and it has no morals or purpose that relates to humans. If the Universe has a purpose (and it might), it doesn't involve humans. We are a product of it, not the other way around.
So how can we make the world fairer? With science. In the past, kids could be paralysed by the Polio virus. That was unfair. So we made a vaccine and now, Polio is almost extinct. We saw that people were being unfairly struck down by smallpox, so we made a small pox vaccine. We saw that people could be killed because they were injured in remote locations, so we invented the emergency beacon. We saw that people might not be born into a well educated family, so we made public schools and invented writing and books to pass down knowledge from generation to generation.
It's not perfect by any stretch - the vaccines aren't always distributed fairly, the public schools are often underfunded and we don't do a good enough job to stamp out illiteracy. But we try, we will try, and we do have SOMETHING to show for our efforts. Polio is virtually gone, and smallpox is (if you don't count laboratory specimens). That's a victory right there. Illiteracy is still high, but it's much, much lower than it was in the past. Hundreds of Millions of people have been lifted out of poverty during the past 30 years. Things are better than they ever have before - and our rising population proves it. For hundreds of thousands of years the human population was very, very small. It has suddenly exploded from less than 2 billion at the start of the 20th century, to nearly 7 billion today. Our technology, our crop growing abilities and our educational efforts have worked.
If I can contribute to this process, in whatever small way I can, I can sleep happy at night.