Somewhere in the middle of the second game (or even the first game), something subtle happens to your skill level. Without any intentional effort, you suddenly notice that results are less than you are used to experiencing in competition. You miss easy shots, simple patterns become near impossible, and you find yourself enjoying the game less and less. Even if you are winning any of the games, it is a struggle to get there.
What has happened is that your sense of fair play has betrayed you. Consciously (or unconsciously), you backed off on your abilities to keep the game a competitive match. The truth of the matter is this: when there is no big challenge involved, there is nothing to speed up your heartbeat. There just isn’t any reason to put a lot of energy into playing as if this match has any importance. You relax your standards, spend less and less time setting up for the shot, even stop your table analysis. Before you know it, it is a major struggle to keep up your attention span. You even start losing games that you should win with your eyes closed.
Even if you realize what is happening and attempt to restore your standard attention to thinking and shooting skills, there is no incentive to maintain your focus. Your game, if possible, gets worse. You can attempt to console yourself that any time on a table is far better than no time on a table. You could quit in self-disgust with only your innate sportsmanship maintaining your courtesy and good manners.
Instead of simply throwing away the time you are using to play against a lower skilled opponent, change the rules of play. Make it more difficult for you to win and force yourself to improve your shooting skills. Give your opponent weight - a lot of weight.
For example, if playing 9 Ball, give the 5 and up. He makes any of those balls, he wins the game. For 8 Ball, you must bank the 8. He can play the 8 into any pocket, you have to play to the last pocket. If you want to get really tough, bank the 8 into the last pocket.
With these shooting skills handicaps, if you want him to take the game seriously, add in another incentive. Offer a buck for every time he beats you. When you have some skin in the game, suddenly, playing every game with all of your attention becomes much more important.
Keep in mind that there is a difference when you are playing against someone you are tutoring and coaching. In this competitive environment, the purpose is not to actually have an actual competition, but spend the time helping your student learning how to make better and smarter decisions.
The net result of the games played is not a matter of who won or lost, but how much improvement was made in your student’s game awareness. Plus, when you let your "student" beat you more often, his enthusiasm for the game is strengthened. This helps him and you improve your shooting skills.
There will be many times when you will play pick-up games at different places. If it is quickly obvious that you are the better shooter, then you need to change the playing conditions. Make it more difficult for you and easier for your opponent. That puts the challenge back into the game and helps keep your edge sharp.