What is life?
Scientifically speaking...I'll agree with energy, whatever name you want to give it. It's been proven that a body looses a small percentage of weight after death, with no dicernable reason we've found yet. (There are some macbre people out there.) And since energy can never be destroyed, only converted....
Why is life?
There are sooo many ways I could answer that one, but I'll keep it to this: Life is a forge, and each person a unique batch of raw materiels. Different talents, different personalities. Different potentials. By going through the forge of life we determine which of those potentiels we will fill. What kind of tool or product we'll be, whether it's a blade or a wagon wheel or a rocking chair. (metal rocking chair? whatever.) Our choices also decide whether the blade will have flaws that lead to its shattering. But the point is, unless we go through the forge we'll never be more than a lump of materials, never be what we could be. It's a risk, but one worth taking.
How is life?
Ideally - lived with honour, courage, and joy.
As for heaven and hell, I personally think people make their own heaven or hell. Someone who never allows themselves to be happy or content in life isn't likely to change once they die.
Death doesn't scare me. Dying, yes. There's lots of ways I wouldn't want to go. But death itself, no. My concern is whether I'll have acomplished what I need to before the plug is pulled.