Practice is only meaningful when it’s done in a context where the trainee is receiving continual feedback from their participation in the real thing.
To be an effective practitioner, you have to ask yourself, “What are my practice sessions preparing me for?” Then you have to go do the thing you’re preparing for, before you feel prepared to do it, and get your ass kicked. After that, reflect on your experience and use your rehearsal period to work on the areas of incompetence revealed by your performance.
If you’re using practice as a way to protect yourself from having your weaknesses exposed, you’re doing it wrong. My favorite definition of learning is this: “the process of doing something that you don’t know how to do WHILE you don’t know how to do it.” This is where mastery comes from.
Practice doesn’t prepare you for the real thing. The real thing prepares you for the real thing. Practice is just a way of reinforcing and refining what you learn from the experience of real failure and real success.