Death is a consequence of sin - it entered the world because of the Fall. But even though we must die, God plans that we really do not ever die at all. Death has been transformed for us by Jesus, the Son of God, Who also himself suffered a terrible death. Because of Him, Christian death has a positive meaning. When we die, God calls us to Himself.
Death is the end of a journey.
We have one life each, and it is our journey towards God, or away from Him. We don't come back for more lives - we are not reincarnated. The Church encourages us to have a case packed at all times. Catholics often pray that they will not die suddenly without having time to think of God and to call out to Him to help them as they die. Almost every day on the news we hear stories of people who have died very suddenly, not expecting it at all - in freak accidents, car crashes, and natural disasters.