Position yourself in a baseline corner. The game starts with both players on the baseline. The server chooses a corner of the baseline to serve from, and the other player positions themselves on the opposite back corner. So if you serve from the right corner of your side of the court, your opponent will stand in the far left corner from your point of view.
Simply put, kids combine the technical analytical instruction with their desire to be comfortable (which is nothing else than the body’s signal of telling you what is a natural way of generating force), while adults do everything in their power to perform the movement “correctly,” even when it doesn’t feel comfortable and it doesn’t produce any natural force.
So, a lot of people are very competitive in everything they try. They want to have the best business if they get into it, they want to be the best at their job when they get it, etc. If you are that sort of person and you look for excellence in your game but do not want to commit professionally to this then it is going to take an upwards of 5-10 years to play at some decent level like club level or USTA sponsored tournaments.