Have you ever had a great idea in bed, only to wake up next day with no idea what it was? We often forget great ideas, and right ideas seldom come when we need them, so think on paper!
“The palest ink is better than the most retentive memory.” - Chinese proverb
With a notebook in your hand, you will find good ideas, interesting stories, and funny lines everywhere. Later, when you need material for a text or speech, you can pick the best of hundreds of ideas.
Also, if you write down distracting thoughts, they won't be forgotten, and you can concentrate better.
So, always carry a notebook and take notes. Remember there is an ink in think!

