Not sure what this will be but rewatching avatar may have kindled some ideas about elemental training other then the ones mentioned in the show. Differnet core values to the elemental bending. Obligatory I don't own any of this.
Water is external powerful and independent. Its very nature is of balance. No ebb without flow, no push without pull. To force it is to invite resistance. To work with it is to master true power.
Earth is immutable. Rock will sit through a day in the same way it would a century. It endures, holds itself unbreaking. To manipulate the earth is to become it. Stong, resistant and patient.
Fire is energy. It is born of the body and with breath it takes form. Fire is an element of control. Without control a spark can become a forest fire. With control it can become protection and a giver of life.
Air is ever evolving and everlasting. You can't attack the air it will simply allow you to pass, moving around you in eddys and currents. To underestimate it however is folly, air is everywhere in everything. Embrace the void and release.
