When writing my entries, I usually pick a highlight of my day, and expand on it.  

For example, I was able to lift more weight in gym, today.  

In my journal, I would write about how it felt to lift the heavier weight, what I learned from the movement, and what I'll do to continue to raise my strength threshold.  

This way, it keeps your entries from being monotonous if your normal daily life is very routine.