Imagine your journal is like your friend and you’re telling them about your day. Write about how was your day, how do you feel, what did you do or what are your goals for tomorrow. These are just a few tips, it’s completely up to you about what to write! The length doesn’t really matter, don’t force yourself into writing too much sentences with many characters, write as much as you feel like, even if it’s just a few sentences. There aren’t are rules here.