The biggest question I receive during lessons is that they can strike the ball well during the lesson but when it comes to the weekend competition, they tend to underperform. The best way to make sure you play well all comes down to effective preparation. More specifically there's a time and a place to work on technique but there also needs to be a time allocated for pre-round warm-up.
If your competition is on the weekend, I would advise firstly to have the lesson early in the week. What you will need ideally is have two more opportunities at the range before your competition.
The first range session after the lesson should just be merely technique based working on exactly what the coach has you doing. If you also have time, doing 10 minutes of mirror drills before you come to the range, will also enhance your range session as when seeing yourself in the mirror, you can get an even clearer picture of whether you are doing the right technique.
Ideally the last range session before your game should be the day before your game with the focus simply on pre-shot routine and tempo. You can have a couple of swing thoughts but keep them as simple as possible. This range session is rehearsing exactly what you would do on the course when lining up to your shot. You should try and have as good as alignment as possible and you should treat every shot as if you're on the course. Another great tip is take the same amount of time each time over the ball.
Lastly on the day of the competition, try and spend at least 30 mins on the range warming up simulating again exactly what you would do on the course. Also spend 10 mins on the Putting Green before you go out to ensure you have the feel of the greens.
If you have this formula every week, you will definitely increase the level of your performance during competitions after having your lessons.