All having sex made me do in the long run is make me want to masturbate more - as I became more lustful and I couldn't have sex more than once or twice every month. Therefore, it seems improbable that one is natural and that the other is unnatural, or that by partaking in one it hurts the ability to partake in the other. Rather, it seems that they are both tied to the same biological processes and are very similar to each other, biologically, ethically, and morally.