What are four "fences" people build in their minds and/or hearts?
As people, one of our main concerns is survival. A prominent type of survival is self-preservation—keeping oneself safe from outside forces that may otherwise be damaging. A specific way to do so is by "building fences" in our hearts and/or minds. By definition, fences are barriers, and barriers are meant to keep things out.
One type of fence that is often used in an attempt at keeping reality out is denial. As humans, we have the amazing capability to convince ourselves of almost anything, including that what we see with our eyes is not really happening the way it appears to be happening. This is the basic premise of denial. In using denial, we make it possible to move past the situation (or to remain submersed in it) without actually dealing with it.
Another type of "fence" that is often powerful is humor. Humor allows one to deflect any possible pain that may be present by joking around. Making jokes is one way to circumvent the real issue at hand and redirect focus. Redirecting focus can be successful in creating a barrier and effectively protecting oneself. The humorous approach can also create an almost-invisible fence, rendering it a formidable barrier.
An extension of humor, especially in the world of "fence-building," is sarcasm. As a society, we have become wholly adept at using irony to convey contempt. In fact, sarcasm is used so frequently in our general conversations that we often don't even realize we are using it. However, sarcasm can provide an advantageous barrier because when employed correctly, it can be off-putting. By nature, putting someone off keeps them out, which is the very basis of a fence.
Lastly, withdrawal represents a plausible type of "fence" in our hearts and minds because it is essentially the practice of removing oneself by turning inward. Withdrawal from a situation is a potent barrier because it is generally immutable. Once the decision has been made to leave (or withdraw from) a situation, it is cogent because it renders the withdrawer unreachable. Putting oneself out of reach is arguably the best form of self-preservation; if one is alone all the time, it's virtually impossible to be put in danger by another.
To survive in this world, it may be necessary to build a few fences in our hearts and/or minds. There are many dangerous elements in our society; some of which can be life-shattering if not kept out. Therefore, denial, humor, sarcasm and withdrawal are efficacious approaches to creating barriers. It would also be wise to follow the advice of G. K. Chesterton: "Don't ever take a fence down until you know the reason why it was put up."