Hey, the word "sexual" implies TWO mates. Because a different word exists for when one creature goes at it alone: "asexual." Learned about it in biology class. Asexual reproduction.
So if you think you're "generating sexual energy" every time you fuck your own hand, you're not. You're generating ASEXUAL energy. But humans can't reproduce asexually, so you're just spewing your horny protein juices everywhere for no reason but to release your own sexual frustration.