Need to keep track of things in the workplace simultaneously? Have a grudge against your enemy in the workplace? Whatever else the reason you want to keep track to stay on top of project deadlines, delegated assignments, maybe vent about your boss privately.
You can keep a diary of each day, including daily, weekly, and monthly summaries. Write about extra things you do around the office, how you help people, show management material, whatever you want. When it comes time for promotions and raises, this journal can become dynamite in defending yourself and proving your abilities.