Answer:
Keeping a diary is a matter of writing down what happens in your life: the interesting and the bad, and your thoughts and feelings about both. Diaries can also be used for very specific purposes. With a diary, you don't have to hold any secrets away from the diary, because the diary is there to help you write what you feel. It can help you get through your problems and thoughts with your own words on that subject.
Hope this helps :)