Diary: Memories Keeper

Why do we keep diaries? What makes us write all our thoughts and memories down? Are we that bored and have nothing else to do but share what's on our mind with our paper friends which won't be able to give a piece of advice or even to respond?
In reality, diaries are quite important chronicles of our lives, they contain our fondest reverie expressed at the very right moment of still being under deep impression of this or that bright event in our lives. Diaries are books where the main characters are all alive and real, us being the main protagonists. Diaries are books the authors of which are nobody but us, that's why all the feelings and emotions described in them are true to life and very real.
Diaries are very precious to us because they also keep an immense amount of our memories – both good and bad ones, they are perfect friends to express our memories and feelings regarding them to because they are faithful and best listeners.
Sometimes people share their precious remembrances with diaries, the ones that they will never manage to reveal even to their closest people. Sharing our memories with diaries is a fine way to keep our reminiscences cherished and to make our hearts feel relieved in case we lack peace of mind overflowed with memories.