Could you be
So, perhaps you've heard of me, the breath in everything,
Believed to be the vital force of all living things. Can translate to "air"
People think I'm energy, though life is what I bring.
Can translate into "life force"
I typically come in two varieties, one dark, one light,
Yin (dark) and yang (light). (From Joe's comment)
Recalled differently in some societies, seeking insight.
Has different characters in different socities https://en.wikipedia.org/wiki/Qi#Characters
I'm used by people of all sorts, healers and fighters,
You can heal with qi and is also a concept in Japanese, Korean, and Chinese martial arts.
To bring you balance, I exhort, used by some writers.
Qìgōng involves coordinated breathing, movement, and awareness. It is traditionally viewed as a practice to cultivate and balance qi.
The acrostic is SPIRIT. Qi is a polysemous word that could also mean spirit.
Title: Luminous beings are we, not this crude matter
Confirmed in another answer that this is part of a quote by Yoda. Yoda is a practitioner of the Force. Qi is a vital "force" for all living things, similar to the Force in the Star Wars universe.