I have a mare that has a "scary place in the rign. There is no amount of collection, encouraged or forced that makes her like it. Since it's been darker and that is the spot in the ring that is under the lights, I finally decided it was time to address the issue once and for all.
What I did was put her on a big 20 meter or so circle that wnet through the scary space. I started by riding her through the spot at a walk. If she was good and non-reistant, I patted her neck and told her how good she was. If she started walking fast, sucking back, resisting my leg or rain aids,etc, I stopped her right away and made her do a turn on the forehand or haunches, stopped, patted her and told her she was good, then walked her on. I kept doing that at a walk (alternating between haunches and forehands) until she walked through in both directions with minimal or no resistance. Then I did the same thing at the trot until I got the same results.
It took about 30 minutes of really patient, consistent insistence on my part, reinforced by a lot of praise when she did good. She still doesn't like that spot in the ring, but she accepts that she has to work there and goes through it with minimal silliness now because she would rather work reasonably through the scary spot than be forced to stand in it and turn around in little circles. Whenever I go in the ring, if she starts good right away, I give her lots of praise and pats as we go through the corner. If she starts silly, turns it is. It normally only takes once or twice now and she is good to go for a full work out.