This is what non-duality means to me at this point in time
Everything I sense in another is actually a part of me that I disowned. When I move up the spiral of development it's very easy to get identified with a higher self and this has an effect of creating a dissociation from lower traits.
When I feel bad I am attacking a part of myself that I have dissociated from. The goal is to do 24/7 shadow integration by noticing an attack (irritation, complaining, condemnation, superiority towards, inferiority towards) and reintegrating that trait by accepting it as part of the body mind in humans - it's just the way life is!
Everything is me, everything I see out there is some aspect of me. Everything is non dual already, but as an ego identified with a particular altitude on the spiral I forget that this is all me and I feel seperate from it. Alienated. And the worse I feel the more alienated I am from my disowned aspects.
That is non duality 101. Shadow integration is not different from non dual spirituality- it is the same thing.
Make peace with what you hate about life and about others, because it's all you. Ultimately even if you cannot feel oneness, it is indeed one.