I used to have a comeback for the cliched expression "Cheer up, life is short." I'd always say "Not short enough!" This always made the person speechless, because he/she never expected to hear that.
There's also a Greek parable about why life is too long and miserable.
Prometheus (rendered as "God" in Christianized versions) created man, but gave him a short lifespan. Other animals, however, complained that their lifespans were too long. Zeus (also "God"), who created animals, knew he was right, and stood by his decision. People knew how to build shelter and use fire to stay warm. One year during a brutally cold winter, a man is sitting inside his house. There's a knock on the door. It's a donkey.
"Let me in, I'm cold."
"OK, but let me have some of your lifespan."
"I accept."
Later that winter, it's even colder. The man is sitting in his nice, warm house. There's a knock on the door. It's a dog.
"Let me in, I'm cold."
"OK, but let me have some of your lifespan."
"I accept."
Spring is slow to arrive. The same man is still sitting in the same house. There's a knock on the door. It's a cat.
"Let me in, I'm cold."
"OK, but let me have some of your lifespan."
"I accept."
Spring finally arrives. The animals leave, letting the man keep the years they gave him.
And so, this is why people's lives are the way they are. Only during our divinely-given years do we live life to the fullest, with a balance of joy and responsibility. During the years we took from the donkey, we just carry the burden of other people on our backs, don't really understand why, and lack the power to stop it (that's work). During the years we took from the dog, we just sit in front of our house, shout at people passing by to go away, and feel overjoyed by gestures of attention/warmth (that's retirement). And during the years we took from the cat, we don't have the heart for anything but lying around the house, hoping our families are nice enough to feed us (that's very old age).