You hit it beautifully for forty minutes on the range. Ninety seconds later you are on the first tee and it has gone. This happens to almost everyone, and the explanation is more useful than being told to relax.
What you actually practised
On the range you were holding a thought. Keep the arms connected, turn more, whatever it was. Holding a thought works fine when the only thing competing for your attention is the next ball on the mat.
On the first tee your attention goes to the group waiting, the water on the right, and the score you want. The thought gets crowded out, and the swing underneath it is the one you had before you started.
Thoughts versus habits
A thought lives in your conscious mind and needs attention to work. A habit lives in your body and runs whether you are watching or not. Everything you do in practice builds one or the other.
Hitting balls while reminding yourself of a position builds a thought. Repeating a motion against a physical constraint until it feels normal builds a habit.
Three changes that help
- Use constraints rather than reminders. If the wrong move is physically impossible, there is nothing to remember.
- Practise more often for less time. Ten minutes on five days builds far more habit than an hour once a week.
- Finish every session with the aid off. If you never rehearse without the constraint, you never test whether the habit exists.
The realistic timeline
Motor habits take weeks, not sessions. Expect three or four weeks of short daily reps before a change holds up under pressure. That is not slow, it is normal, and it is why the golfer doing ten minutes a day beats the one doing three hours on Saturday.