Perhaps an open mind is overrated.

We hear a lot about the benefits of having an open mind. From Thomas Dewar realizing that "Minds are like parachutes -- they only function when open," to Charles F. Kettering remarking, "Where there is an open mind, there will always be a frontier," there is no shortage of inspirational quotes that could underline the significance of keeping your mind open.

But what about making a more concerted effort to keep your mind closed?

In Napoleon Hill's, Think and Grow Rich, the best-selling author dedicates a whole chapter to the steps necessary for developing persistence. Among these are having "a definite plan, expressed in continuous action," as well as making sure you have "a friendly alliance with one or more persons who will encourage you to follow through with both plan and purpose."

As Hill stresses the importance of maintaining "a definite purpose backed by a burning desire for its fulfillment," he also makes an often unheard of case for a closed mind.

According to Hill, "a mind closed tightly against all negative and discouraging influences, including negative suggestions of relatives, friends, and acquaintances" is absolutely critical for fostering perseverance, something you will need in your journey towards success.

Naturally, the closed mind Hill is talking about does not mean the closed mind you may know and recognize. Rather than sit with a closed mind that is firmly unreceptive to new ideas and opportunities, instead value the closed mind that blocks itself off from negativity and discouraging comments.

If you allow your mind to be too open, you may absorb all that is around you -- and none of us are surrounded by positivity at every second of the day. Sometimes we are around people who are not motivated or by people who belittle our goals. But if your mind is closed tightly against these negative influences, they will hardly be a problem for you on your path to achievement.

In order to develop a persistence that keeps you focused, maintains the strength of your willpower, and does not leave you feeling defeated, keep your mind open in some ways, but don't forget to keep it closed in other ways, too.