to make it brief.
Nature really doesn't really care what happens to you after you reproduce. That is the meaning of life pretty much.
That being said-
Asexual reproduction is awesome because one cell can separate many times over a short period of time.
Although sexual reproduction takes longer, it allows the offspring to have a more diverse set of genes than it's parents do. This can make an immunity to a disease stronger.
That is where asexual reproduction fails. If one disease can kill a cell that uses asexual reproduction, it can kill all its offspring because they all have the same dna.