Deciding what to hit moments before hitting a ball leaves you open to making crazy decisions. Having a gameplan allows you to focus on that. It might not be the best gameplan against that particular player but that’s not the important part. Having or developing self-control can be the difference between winning and losing. Every now and again, pick a gameplan and use it in a match. Keep with it until the end of the match. That last part is important. It builds mental strength. I remember a student of mine playing a club match, she was the number 1 string and hers was the last match. She lost the first two games and we changed the gameplan to something that we thought would work. She won the next two game, making it 2-2. In the final break, she said she was going back to playing her way because she thought she could win. I tried to convince to stick to the gameplan. She changed the gameplan and lost. Maybe she would have lost even if she hadn’t changed the gameplan but I don’t believe so. Once you have decided on a gameplan KEEP USING IT. You might not win each match with a particular gameplan but by trying to plan each point as it happens will be worse. https://youtu.be/hTXG-0tugUU
Is a Bad Gameplan Better Than No Gameplan? I believe so. Knowing what you are going to hit a long time before you hit it, can keep your mind clear and that process of avoiding distraction can make that shot better.