If you are in the lead, maintain that lead (don't slack off just because you are a few points ahead). If you are behind, ignore the score. In this game it is still possible to recover from a 10-19 score, if you maintain focus. When you make a mistake, acknowledge it and move on, don't fixate on it.Whenever I make a mistake, I usually tell myself something like "Okay, don't do that" or if it's a tactical error, I remind myself "Don't do that because ___".What helps me the most is having a game plan at the start of the match:Ex. for singles: "Okay, I know she's weak in moving front-back and has poor defense on her backhand so I will try to do place 2 shots in the rear court then one in the front, or I will attack her backhand more" Ex. for doubles I usually just set myself shot/placement goals "I will try to push or drop off of the serve" or "If I play front I will cover the straight reply".If your game plan does not work, revise it during interval at 11, or sooner if you are able to strategize midmatch. Always take the interval if you are behind to mentally collect yourself and get your focus back.Hope this helped!