Here are notes from Sam Horn's session on Concentration from September 15th, 1981. Still great advice to this day!

* Concentration defined; voluntarily focused attention.
* Discipline of ignoring irrelevant matters
* Fixing ones' powers, efforts, and attention
* Most people work best under a deadline; when their concentration is focused.
* Fatigue is a big road block to concentration

This last note is telling!:
* Society is moving towards a lower frustration tolerance with less discipline, and more need for immediate gratification. These are detriments to concentration.