Back in the early days of computers, every second of computing time was considered precious. On mainframes, users were billed for the CPU time their program used. Computing time was horrendously expensive, so people wrote their programs to use as little of it as possible. Each program was run in sequence (or "batched"), and when the computer got to your program (stored on punch cards or paper tape), it performed the task quickly then sent you the bill.
Today, computing is ridiculously cheap. Today's personal computers can do more that a multimillion dollar room-size computers a few decades ago, so no one thinks much about CPU usage. As long as your own computer has sufficient capacity for the task at hand (say, the word processing program I am using now), no one cares how efficient the program is or what empy processes are running in the background.
Unfortunately, the same oversupply of computing power does not apply to the human brain. If you think of the brain as a biological computer, its physical capacity hasn't changed in thousands of years. "CPU time" is still extraordinarily precious. Everything though you think takes time. You have think about things sequentially—first about one problem, then another—and at the end of the day, there are only a limited number of thinking units available to you. The physical machine also has a limited lifespan—longer that a typical PC but certainly not infinite.
In your own universe, your brain is the most expensive and valuable mainframe you have. Why, then, would you want to throw any of its capacity away?
People can be very efficient with their thinking time when they are focused on an important task, like writing a report or bringing an airplane in for a landing, but as soon as you give them the freedom to use their brain time as they wish, they seem intent on wasting it.
It is not a waste of brain to just sit and think, as long as the topics covered are important. Daydreaming is not necessarily a misuse of the brain's CPU time either, because that's often how you solve real-world problems. There is nothing wrong with staring into space and free-associating, because this is the way we process our past experiences and plan our future actions.
What is a waste of mental resources are all those millions of outside products and diversions that do nothing for us except soak up CPU time. Crossword puzzles and video games are prime examples. Vast swathes of brain time are absorbed by these devices with nothing to show for them in the end. Come to think of it, just about everything marketed as entertainment is a mental time waster of some kind. People are always seeking "stimulation" in their entertainment—that is, a high occupation of mental resources—but it isn't usually meaningful stimulation that contributes anything to their lives.
It seems as though most people want to waste their own brain capacity. They drink to avoid using it. They "party." They watch meaningless TV shows for hours every day. They have those iPod thingys stuck in their ears at all times so there's no possibility of any conscious thought intruding.
Perhaps this is the most destructive addiction of all: the addiction to thought avoidance.
This disease manifests itself as "boredom" whenever ones mental time isn't fully programmed. Boredom is like the smoker's craving for a cigarette or an alcoholic's lust for drink. As soon as most people have "nothing to do," they panic and try desperately to fill the mental space with something.
And it isn't just video games that fill the void. A voracious reader can be just as much an addict. Is he reading because of the real benefit he is getting from the content or because of the anxiety he feels whenever he sits alone without anything to process?
Why do people avoid their own thoughts? Perhaps it is because those thoughts keep leading them to unpleasant conclusions. If you feel, deep down, that you are worthless or have made mistakes you can't deal with, your unhindered thoughts are always going to lead you back there. If you keep your brain continuously occupied, then you never have to think those thoughts. When the amusements run out, though, that's when panic strikes and you look for something, anything, to keep the bad thoughts at bay.
If you care about doing something useful with your own mental capacity, you can't be swayed by boredom or panic. Instead, you must only do things with your brain time that make sense. Like CPU time on a mainframe, your "thought space" is something you need to protect and never waste. Like any other precious resource, it has to be carefully managed.
You can never tell your brain exactly what to think, but you can manage the environment in which it operates. If there is too much clutter in that environment, you're not going to get a lot of useful thinking done. If you are constantly being interrupted by outside stimuli, it is going to be difficult to accomplish much complex higher-level creativity. If you turn off the radio, remove the Bluetooth from your ear, turn of the laptop and withdraw temporarily from people, the quality of your thinking processes will probably improve.
Those are exactly the conditions that most people equate with "boredom," but if you are wise, you will learn how to work with boredom and make it your friend. Only by being comfortable with your own thoughts can you make the most of your brain capacity.