What does it mean to be united in yourself?

Speech is constante—or at least tends towards continuity. It is the outward expression of the spirit, therefore it is constant, like the expression on a man’s face, which is the outcome of his constant character. When a spirit is purified and becomes holy, one, united in himself, He ceases not to cry day and night—Holy, holy, holy.

Not holy am I, but holy art thou, O Lord, towards whom my being ever tends.