Golfers who struggle with accuracy on tight courses often get distracted by thoughts of the trees rather than concentrating on where they want to hit the ball. Invariably, wherever your thoughts go, your golf ball follows.
The brain is incapable of registering the word 'NOT' so if you tell yourself NOT to hit the trees, all the brain remembers is 'trees' and will do exactly the opposite. Instead concentrate on what you do want to do.
Playing on a tight course is great for improving your accuracy - it forces you to focus all the more intently on where you want to hit the ball. Try picking a small, specific target before where you hit your ball - for example the highest tip of a pine tree behind the ball. The tighter the course, the more specific your instructions need to be to your brain and body about where the ball should be.
Even on a more open course, aiming at specific targets will improve your consistency and scoring.