Other forms: journals; journaling; journaled
If you keep a daily––or at least somewhat regular––written account of your life, you are keeping a diary or journal. A journal is also a periodical, such as a scientific journal or a scholarly journal.
Journal comes from an Old French word which meant daily (jour being the French word for day, as in soup du jour, or “soup of the day”). You can keep a journal in an old notebook, on the computer, or on scraps of paper, but if you keep it in a book made especially for that purpose, then that physical book (whether you've written in it or not) is called a journal.