Adding the element of the course with different lies, obstacles and the pressure of a scorecard, will have an effect on your swing.
Tempo can change and will your technical work hold up under pressure?
If you're struggling, a few changes might be needed. Here are the two biggest (often mistakes) I see:
You should be avoiding any technical thoughts, you're not trying to improve your golf now, you're trying to see where the ball is going today!
Pre Shot and intent
You should have a pre shot routine and usually any movement should be consistent and help produce the shot you want to hit. Over the ball there are options, do you think of a position? The ball flight? or nothing? This is as much of a skill as the swing itself so get practicing and see what works best.