A logical presentation of my views on the afterlife and, with this, a brief explanation of the meaning of life.

As concisely as possible, I think that spiritual afterlife, if it exists, is completely similar to physical afterlife. Unless the body is cremated or buried in a steel coffin, it will return its nutrients to the Earth as a system (rather than simply a planet, the Earth as the planet and all things which live on it) through decomposition and providing nourishment to the various bacteria, fungi, and scavengers which descend upon a corpse after death. This seems gruesome, but it is really a beautiful system of recycling. Death nourishes life, which, in death (and even possibly in life) will nourish other life, and so on and so on. I suspect that, after a sufficient amount of time, the nutrients contained within the physical form would be spread through every system on Earth. This happens to every piece of organic matter that doesn’t undergo flash-fossilization or petrifaction or something similar. Accepting this, there is no reason to assume that the spirit or soul would not undergo the same process.
The soul would necessarily have to be organic, just as every living thing known to human science is. It should follow, then, that, just as everything organic does, one’s soul will eventually die. I assume that this occurs at the point of the cessation of bodily functions. If this can be assumed, it is sensible to assume that the soul undergoes the same process as the body. It decomposes, returning its nutrients to what would probably equate to the spiritual equivalent of bacteria, fungi, and scavengers, which must, in turn, go on to feed other forms of spirit and so on. This provides the purpose of life: to beget life. Note that I am not saying that the spirit must exist; there is no reason to believe this. However, the purpose of life remains essentially the same. The possession of a soul is not necessary to fulfill one’s duty in the afterlife.
If, in death, one provides nourishment both physically and spiritually, then, unless he or she is an apathetic, selfish, or generally unpleasant person, it should follow that s/he would want his/her body and soul to be as nourishing as possible. This is not a real issue, though, because the things which provide such sustenance are things of which most people enjoy partaking. Provide the body with proper sustenance and it will doubtlessly provide those which recycle it with proper sustenance. Provide the soul with proper sustenance and it should, as the body does, provide those which recycle it proper sustenance. It seems that the nourishment for the soul consists of knowledge, wisdom, or positive experience in life. Just as an unfed or chemical-ridden body will be less sustaining to most forms of life than one which is fed, a soul which has been fed with only negative experiences will certainly provide less sustenance than one which has been fed with positive experience.
My message: eat well and enjoy life, not only because you enjoy it but because it will benefit life (planetary, at least) as a system.