I think that since Tojiko has onryō roots, she is actually pretty emotional and has pretty drastic mood swings. And so, she meditates a lot. Maybe even frequents Byakuren's or Kasen's place for that.
Actually... wait a minute. The only source that calls Tojiko an onryō is Akyū in the Symposium. Everywhere else, she's a ghost like Yuyuko. So I suppose ZUN's idea is that she's a ghost who used to be vengeful?
Also... unless Akyū was mistaken, Tojiko's lightning ability is not a Soga family thing too (which on the contrary can certainly be the case). Tojiko's lightning comes from the simple fact that she's an onryō – it's a racial ability. This means Mizuchi should be able to use lightning as well.
Lightning seems to be equated with anger in Touhou.
