On Self-Preservation...

Self-preservation is an instinct, is the first law of nature.

Any organism will strive to make sure that it stays in place, in a comfort zone, in an environment where all it's basic needs are met.

Does this too justify the human need of self-preservation?

Or is it a convenient excuse to greed, arrogance and deceit?

In the psychological and physical sense, what makes people different from a parasite, which lives off a host; sucks the life out of it then leaves to find another that will satisfy it's need?