If you analyze any win on the PGA tour, and even your own best score, you will find there is always a component of randomness attached to it. What I mean by that is you can prepare and practice all you want, but there will always be a bounce that goes your way, a putt that drops that shouldn’t have, or a sudden collapse by an opponent who seems destined to win. Things happen that you simply cannot control. That's why the best performers prepare for anything and everything.
Switching to another sport to drive home my point, Dan Coyle, author of the best-selling book, “The Talent Code,” tells the story of LeBron James setting an off-season goal to improve his game. James ruthlessly analyzed his weaknesses and set out to build a new skill set that would make him a better teammate. He hired a master coach and became a humble apprentice, breaking down his training sessions in order to learn new scoring moves.
In a nutshell, this is what the best do. You can take the same approach with your own golf game. Hire a coach, break down your weaknesses, then create a plan that focuses on those issues in detail. Spend your practice sessions eliminating your issues and then put your newly acquired skills into practice on the golf course as often as you can. And be sure to get feedback so that you can check your progress.
Check out TPI's article: Stuff Happens in Golf