1) The first bit of advice is to recognize that you, like almost everyone else who discusses "the 10,000 hour rule" (and what it means regarding "practice" and "mastery") have completely failed to understand what the actual author meant, so you do yourself and everyone else a favor by dropping the subject.

2) The second bit of advice is to examine this "reality" thing. You can, obviously, switch careers anytime you want. Only you can define what "success" in that career will mean for you, what investments will be required in order to achieve it, whether you will enjoy the process, whether you are asking the impossible of reality (a very short, sedentary, middle aged person just isn't going to switch into the "Professional NBA Superstar" career), and so on.

3) Your life expectancy is, what, roughly 80 years now? You've spent maybe 20 or so on your current career. You've got twice that remaining, theoretically, and you're concerned about time having run out already?

All this is a roundabout way of saying your own attitudes toward all of this are the main, though not the only, challenge you'll need to address provided you are not asking to violate physiology/etc.