Life is just a particular arrangement of matter that can keep producing copies of itself. Maybe you're asking about consciousness?
Consciousness is the amalgamation of a sentient organism's sensory perception of the world around it. What you see is not what's there, just an image of the light that is reflecting off what WAS there a nanosecond ago (or in the case of stars, a million years ago).
Death is the natural order of things in the universe. Life and consciousness are an oddity.
Nobody can be happy without believing an illusion. Knowledge of the truth bears no happiness beyond allowing for more elaborate illusions. That illusion might be that after we die we will be remembered or that we accomplished something longlasting. This is an illusion because even if we did, we wouldn't be aware of the result of it, because we're dead. The thought that we will be remembered or that our life mattered keeps us happy in our last moments.
But dying happy is also an illusion, what is the ultimate culmination of a few seconds of happiness in your long life? And what does it really count for once you're dead? You won't remember it, because you won't exist after it.
Some people go with the illusion of a loving god or an afterlife, comparatively simple illusions because they don't demand inquiry or deep understanding. Some people (like me) go with the more elaborate illusion of understanding the nature of life and death through science. But we aren't actually observing the physical universe as it is, only as we can perceive it. Objective truth is ultimately unknowable through the scope of a subjective consciousness. We like to think that it isn't though, and that's where the satisfaction of scientific enquiry comes from. The illusion of objective truth.
So life and consciousness, being the only things we've ever known as sentient beings, subjectively end up being a quest for happiness; and happiness can only be brought about by an illusion. So pick whatever illusion's complexity goes with your inquisitive demands; the simple illusions will satisfy a layman, but not a skeptic. That's what life is to me.
Objectively, life is meaningless, fleeting and ultimately counts for nothing when the universe dries up. But who cares about the objective universe? It's not like we exist in it.
