The Biblical teachings on the fleeting, ephemeral and temporal nature of earthly life are easily, but mistakenly exaggerated into an attitude of indifference or devaluation of earthly life. This violates the Scriptural teachings that earthly life is of great value, as something created by God and loved by God. Such an exaggeration is seen in Gnosticism, an early Christian heresy, as well as in some Eastern religions that emphasize fasting and rigorous asceticism. This exaggeration can also lead to religious zealotry and fanaticism in which people may become violent against themselves and others, thinking that a) this earthly life doesn't matter; b) they will be consoled in heaven. They will be sadly mistaken.
One of the reasons this kind of exaggeration occurs is due to the ambiguity in the meaning of "earth" or "world" in the Greek New Testament. The NT literature uses the word "kosmos" (world, cosmos) in two ways:
1) as mankind, the realm of earthly creation that God created, sustains, loves and comes to save;
2) as the fallen world-system or idolatrous/secular/legalistic cultures of this age, which God comes to judge.
Christians are called to separate from the fallen, sinful world cultures, but not to attempt to separate from mankind itself, which is unrealistic and not compassionate. We are to be in the world, but not of the world. And there is certainly no justification for violence against human life, which God loves and comes to heal and save.
All thoughtful people should ponder the incredibly rare and precious and wonderful thing that is earthly human life. Scientists study it all their lives, and only scratch the surface of its complexity. They search the galaxy for other worlds, and find none like earth. How far would one have to travel to find a place like earth? It might be forever. And every blade of grass, every little bug, is just as rare in the universe as we are. Life in this cosmic perspective is far from cheap. Likewise from the biological perspective, our bodies are wonderfully and awesomely made. Physicians study the details of the body and yet know so little about how it works. We should never take bodies for granted. We are made of dust, but God has made it come alive and thereby the universe has become conscious of itself!