I think that we can all agree that the man, Jesus Christ, possessed a human center of self-conscious reality (self) through which He related to the Father in prayer, worship, adoration, and love.
In my opinion...
Trinitarians want to make this distinct human "self" a second "divine person" that pre-existed the incarnation.
Modalists want to make this distinct human "self" the same "self" as the Father, albeit existing in a distinct mode of existence.
I see problems with both Trinitarianism and Modalism. One makes the "self" of Jesus Christ a second God... the other makes the "self" of Jesus Christ merely an illusion necessitated by mode as it relates to nature. Thus Jesus appears to be a distinct human person in relation to the Father... but He isn't.