So, assuming that tantra actually does something for its practitioners - a fact that many seem convinced of, so it cannot simply be disregarded - what is a non-mystical explanation?
Let's look at one classical instruction (for guys - it's actually the one I practice the most):
"Focus on your breath. Upon inhaling, breathe as deeply as possible into your pelvic floor. upon exhaling, clench your PC muscles and direct the energy from the sex chakra up the spine."
This roughly translates to: "Focus inward - feel your breath - feel its flow - breathe deeper and deeper now - and as you go deeper and deeper inside, disregarding conscious thoughts that only come in the way, relaxing and feeling those good feelings, notice how the energy flows..."
To me, this sounds suspiciously like a trance induction. I'd hazard the guess that that's what it really is. Shifting the focus around inside your body helps to abandon verbal thinking, thereby driving you deeper into the trance. And of course, clenching the PC muscles does have a physical effect and produces sexual feelings, because it massages your prostate, and because the anal area is an erogenous zone (even if many males don't like to admit that).
As an experiment, you can try focusing the breath on totally unconnected areas. I don't know about you, but if I inhale into my left leg, and then exhale into the right leg, I get pretty much the same results. If that's not quite as much fun, probably that's because focusing on the organ that is producing those delicious sexy feelings is the best way to intensify those feelings?
I think we might be on to something here. No voodoo involved, no hindu gods invoked, no transcendental energy fields presupposed.
It simply makes sense, that's all! I strongly feel that this practice makes me stronger, that I'm actually more energetic and have more willpower if I do not ejaculate, but practice tantra instead.
This factor remains unexplained, for the time being. I have no frakking clue why not ejaculating makes me more energetic. If I had to guess, I'd say it's simply because I'm more horny, and tantra is a clever way to sublimate this horniness into useful actions.