When you write, your expressing yourself.
Whatever your feeling at the moment. Your words speak out in a tone of hurt, sad,happiness,grateful,thoughtful.
Writing may help release stress that's inside of us. Our hearts. Our minds. Our thoughts.
Whoever the reader is, they can tell what your feeling in that particular moment just by the way you wrote each word and sentence. It's like your speaking to someone that's not actually there.
Writing and expressing yourself is a good thing to do. You can let everything out that was once buried inside of you.