According to Christianity, death opens the door to eternal life.
Jesus has died on the cross to offer all humankind the opportunity to live forever, without suffering and earthy problems. Death is not feared by the true Christians because they have a clear understanding of what will happen to their souls after the death of the physical body: their life will be analyzed and if they managed to live righteously, to follow the commands of God, and were the true believers, their souls become eternal. Paul has devoted many verses to teaching the believers about earthy life, death, and life after death. He notes that it is important to be dead to sin but be alive to God. It means that humans must resist the earthy temptations which take them from God and they should take care of their souls prior to death.
Sin plays an important role in understanding the Christian view of death. Sinful people (with evil desires, angry emotions, and shameful deeds) who are not willing to accept faith into their hearts will not be saved and their soul will die with their physical body. Death and eternal life are two different concepts. From one side, death is the only way to eternal life. From the other side, death of the sinful person is the end of his existence.