I am using journaling to help combat depression and I pick one (or more) of the following, depending on what I did that day:

• What are some things that I accomplished today? It does not have to be significant things, just things, no matter how small, even if it is just a step in a larger process.
• Was there a time today that I felt a social connection, like a good conversation or a shared activity?
• What is something I did that was fun?
• What am I looking forward to?

Overall, I only spend a couple minutes each day on it, but the process of thinking about what to write down lets me end each day feeling good about something.