Simona Halep finally overcame her past problems in Grand Slam Finals and won the French Open. She has been the number one player in the world for some time (which seems a little crazy since she had not won a Grand Slam) but has had a difficult time with that last match in the majors.
The biggest difference in her game at the present is how she is dealing with adversity and her tendency to be extremely tough on herself. Her approach in the past has been to get very down on herself if things started to go wrong on the court and really beat herself up mentally and emotionally. This actually led her coach, Darren Cahill, to step down last year. He had tried over and over in his communication and coaching to emphasize the positive and help Simona look at things differently when she was in the heat of the battle on the court. He realized that this adjustment to her thinking was the difference. Darren returned as her coach and although there were signs of improvement, Simona was still getting in her own way at crucial times in her matches.
At the Australian Open this year when she survived a couple of brutal matches and gave a great showing in the final against Caroline Wozniacki, it was starting to come together. In the French Open Final, she lost the first set and was down a service break in the second to Sloane Stephens and then became even more determined, rather than falling into her negative mode as she had in the past.
Her ability to be positive even when the initial outcome of the match was not optimum, was the difference this time. She gave herself a chance to win even after that disappointment early in the match.
Try to focus on the present and where you want to go rather than on what has already happened. This positive attitude will enable you to hit the shots you need to give yourself the best chance to win the match.