Originally Posted by Topspin Shot
In matches, assuming you want to win, don't hit a shot that you aren't confident you'll make. This does not mean push, but it does mean don't aim for the lines, and don't swing so fast that your stroke breaks down.
There's always a gray area in confidence, meaning it's never a yes or a no. There are many shades of maybe. So, it's a matter of observing your skills and calculating your chance. If you're 90% consistent and too comfortable and the match is drawn out too long, you're not playing your best. You should only be a little more consistent than your opponent and to win as fast as you can. He'll go home and rest but you'll have to play better opponents. That's why.