Ultimately, there is no way to be sure that the so-called right decision has been made before it has been made and acted on. All you can do is ensure that the process of decision-making is deliberately and painstakingly executed. That doesn't guarantee the best decision, but it sure makes it a lot more likely.
What's going on that a highly skilled athlete can suddenly and inexplicably lose the fundamentals of fielding? The usual explanation is that these players start to "overthink" their automatic, highly tuned visual and motor skills, and sabotage them in the process. But this has never been proven, nor is it clear just what this means on a basic cognitive level.