What's the most important point in table tennis? The next one. It's that simple. And yet players constantly fret over the previous point, the one that's over and never to be replayed. As far as you are concerned the next point is for the gold medal at the Olympics. If it's a practice match where you are working on something, you might ease up tactically so you can work on specific shots or tactics, but other than that, you should go all-out every point.
Jan-Ove Waldner, considered by many to be the greatest player of all time, was once asked what his greatest strength was, and his answer was that it was his ability to always consider the next point the most important point of his life - and play it as such. If you make this a habit, two things happen. First, you always play your best. And second, you get so used to playing "the most important point of your life" that when you do play a big point, you are used to doing so. And guess what? You'll be so used to it you won't even be nervous!