你将跳蚤放进一个带盖的罐子里。它们在里面跳的时候会一次又一次撞到盖子。当你观察它们跳跃并且撞到盖子的时候，你会发现一件有趣的事情，跳蚤会继续跳，但是它们不再跳到能撞到盖子的那个高度。然后， 当你拿下盖子的时候，尽管它们仍在跳，但是它们不会跳出罐子。我重复一遍，它们跳不出去是因为它们做不到。原因很简单，它们限制自己只能跳这么高。一旦它们限制自己只能跳这么高，那么这也就是它们能力的极限了。
　　You train fleas by potting them in a jar with a top on it. Fleas jump, so they will jump up and hit the top over and over and over again. As you watch them jump and hit the top, you will notice something interesting. The fleas continue to jump, but they are no longer jumping high enough to hit the top. Then, and it’s a matter of record, you can take the top off and though the fleas continue to jump, they won’t jump out of the jar. I repeat, they won’t jump out because they can’t. The reason is simple. They have conditioned themselves to jump just so high. Once they have conditioned themselves to jump just so high, that’s all they can do.
　　很多时候人们也是一样。他们自己限制自己，从来不去开发自己的潜力。就像跳蚤一样，它们没有能够跳的更高，还以为自己把自己的能力发挥到了极限。
　　Many times, people do the same thing. They restrict themselves and never reach their potential. Just like the fleas, they fail to jump higher, thinking they are doing all they can do.