My Enemy and Friend

This person is someone I've seen time and time again
And someone that I don't even know.
Sometimes they are my best friend.
Then on other days they're my worst foe.
This person encourages me and tells me I can do anything.
Then they tell me to just give up on the race.
They tell me not to worry about what other people think.
Then they laugh at me right in my face.
This person blesses me with kindness and love.
Then they curse me with cruelty and hate.
They act like an angel sent from above.
Then they become a demon sent right from hell's gates
This person is sometimes my enemy.
This person is sometimes my friend.
They humiliate and discourage me.
Then tell me I can make it to the end.
This person dries my tears when I cry.
Then they cause them to the point that I can't even see.
This person is at war with me all of the time.
This person is'..me.