Dang it! How'd I miss that?!!! I can't play! These (or perhaps harsher words) are the words of a player who is trying too hard, i.e. pressing too much. This is also true if you feel like saying these things during a match but hold back. They are symptoms of a player wants to win so badly they can't play well, and so don't win nearly as often as they could.
Instead, learn to play with a more relaxed attitude. This doesn't mean no emotion, but only positive emotion. The more negative emotion you have, the less confident you'll be, and the harder it will be for your subconscious to do the things it's been trained to do, i.e. play table tennis at your "normal" level.
When you do feel these negative thoughts, there are sports psychology methods to overcome them. However, it's far, Far, FAR better to play with an attitude where you rarely face such thoughts during the match.
You do want to try hard, but in a different way. You should be fighting physically and mentally. But you should be battling an opponent, not yourself. Instead, focus on individual points, think simple tactics, and let your training take over. Have fun, stay cool, and you'll maximize your chances of playing your best - and yelling, "Yes!" at the end.