I know we hear stories all the time about Shaq and Ben Wallace being able to sink 50 free throws in a row during practice but I have my doubts. If free throws were THAT easy for them during practice they wouldn't look so uncomfortable and clueless during a game.
The "I'm really good in practice, but not in games!" thing is bull . It's like people who say "I'm really good on the driving range, but I never play well on the course!" Yeah, no , you're swinging well on the driving range when you have 100 balls to hit one after another so you can identify flaws and focus on correcting them because it's just practice. Same thing with basketball. When you're shooting hundreds of free throws in a row and can get in a rhythm and think about form/motion. The whole point is to practice them to the point where they're 2nd nature and you have the right form/motion without thinking about it.