You seem to be saying you have some fixed amount of life energy or you're dead, but why couldn't we have more or less "life energy," comparatively speaking? If we look at light as a possible analogy: sure it's either light or it's isn't, but you can certainly have more light in some places than in others. Some folks do seem to burn brighter than others...at least, I've heard this from enough different people to consider it a compelling idea.
We know from physics that energy cannot be created or destroyed. So if we are increasing our life energy, where is is coming from? And if we are decreasing our life energy, where is it going?