You train fleas by putting them in a jar with a top on it. Fleas jump, so they will jump up and hit the top 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.
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.