Indians

I think the song is about hard drugs or hard psychedelics, and the use of them to escape reality. He says that he is riding a horse that cleaves through the air and space of dreams. This could represent the dreamlike nature of psychedelics, the loss of consciousness, lack of awareness of himself and reality while in the psychedelic world. In this “world of light,” he realizes that he is not truly there, indicated by the lines, “And it's coming over me That I'm not here I am on another plane Jumping around, hit myself I returned inside of me…” This may signify the projection of consciousness to a different life through the use of psychedelics. I believe he jumps around and hits himself to bring himself back to reality and further conceal the barrier between it and his psychedelic experience. Tears slide down his face as he has to come to terms with reality. He realizes he’s not who he thought he was, the life he lived in his psychedelic experience was untrue.

[Edit: Added some words to help understand a little more]