There’s an interesting eastern model of magic, popular in Buddho-shamanic syncretic religions. Windhorse is a little bit like mana, but not quite. It’s based on positive karma, and you charge it like a battery by doing good things. It’s not like “energy” in the New Age sense; more like “authority.” There are prayers and rituals to increase Windhorse, but you can also increase it by doing good deeds, or by acts of austerity. The idea appeals to me.
In my own speculations, it’s a feeling of lightness and power that centers in the solar plexus. I often feel it spike after magic, or after work (keeping in mind that I very much enjoy my job and feel as if I’m doing some good). It can also be transferred to another, it seems, and doing so actually increases it. That would imply that one could become a big burning ball of Windhorse, giving it to all and sundry. But some things kill Windhorse.
For me, negative speech saps my Windhorse, as does fear. Routine seems to take a lot out of me, as does dirt (which, since I’m not the neatest person in the world, says something). Weirdly, extended isolation also hurts my Windhorse — weird, because I’m a tested introvert and isolation is one means used by shamans to increase Windhorse.