Horizontal Life Balance is quite simple. For us to have what is usually termed "work/life balance", we need to be active in three dimensions of our lives. These dimensions are Work, Play and Growth.
All three are aspects of who we are. To exclude one of these dimensions leads to being emotionally, intellectually, socially and spiritually shortsighted. We need to Work, Play and Grow to have a true, genuine horizontal balance - a balance between spheres of living - in our lives.
This idea appears in other forms in the works of Ken Wilber ("The Big Three"), Plato ("The Good, the Beautiful, the True") and - especially - Hannah Arendt's magisterial The Human Condition, available here:
https://www.amazon.com/Human-Condition-Second-Hannah-Arendt/dp/022658660X
Fred Davis is the teacher I mention in the video: @FredDavisNonduality
https://www.jpjakonen.com