Write about something that doesn't get better.
The pain doesn't get better. You will never learn to truly heal, only accept it and move on. The pain will be put in the past, but as soon as you resurface it, it will never truly get better. You can easily fall back into the past, simply because it left a wound in your heart that will never truly healed only moved on from. That is why it is important to move on from the past, and focus on the now.