My Journal is the simplest journal app you will find anywhere. Everyday you open the text editor an entry is automatically created for you with todays date. You can write a few lines highlighting how your day went or paragraphs describing every event in details.
You can also give each day a rating out of 10 and see how good or bad your days have been using a line graph that represents the rating of each date. This app offers a very convenient way to keep track of the quality of your days and relate mood swings to events that occurred in your life.