Wikipedia describes planning as such:
Planning in organizations and public policy is both the organizational process of creating and maintaining a plan; and the psychological process of thinking about the activities required to create a desired goal on some scale. As such, it is a fundamental property of intelligent behavior. This thought process is essential to the creation and refinement of a plan, or integration of it with other plans, that is, it combines forecasting of developments with the preparation of scenarios of how to react to them. [emphasis added]
In short, planning is the process of identifying a goal and the means for achieving that goal. It is a process of thinking long-term, projecting the results we wish to achieve, and the means by which we will achieve them. It is, as Wikipedia says, "a fundamental property of intelligent behavior" because planning recognizes that we do not live merely for the moment, but for a lifetime.
But planning is not merely a process of randomly selecting some goal, nor is it a product of wishful thinking. It requires much more than pursuing some momentary urge or desire. It requires thinking in principles, for principles are the means by which we project the consequences of our actions.
In our personal lives our planning is based on our individual values. We select the goal and the means for achieving it on the basis of our values and our own judgment. We select the ends and the means. And our means must involve the voluntary cooperation of all involved, whether it is starting a business, or investing, or choosing a career path. We cannot force customers to purchase our products or services; we cannot force others to sell stock to us at a low price or purchase it from us at a high price; we cannot force an employer to hire and promote us.
In contrast, public planning is the product of consensus and compromise. The public does not speak with one voice--individuals have different goals and values. Public planning cannot represent all of these individual goals and values, for they are often contradictory. The result is some middle ground that attempts to satisfy the largest number of people.
More importantly, public planning--both the ends and the means-- is imposed by mandate. Those who do not agree with the plan must abide by it. The planning of individuals is rendered moot, for any individual plan must conform to the public plan. The judgment of the individual is negated.
Some argue that public planning is necessary in order for the government to address infrastructure needs, such as flood control, road construction, and utility installation. But such arguments are based on the faulty premise that the government should even be involved in developing a city's infrastructure. Government's proper function is the protection of individual rights, not building roads, dredging ditches, or laying sewer lines.
In past years, Houston's zoning advocates have argued that zoning is needed to plan the city's development. Otherwise, they declared, the city would develop in a chaotic manner and become unlivable. More than sixty years have passed since these dire predictions were first uttered, and Houston's population and economy continue to grow. The voluntary choices of thousands and thousands of people are clear evidence that the pro-planners were wrong--Houston is eminently livable.
The fact is, it is the private plans of millions of people that make the city livable. Each of us can plan and act according to our own values, rather than being compelled to follow some master plan. And this is precisely what the planners want to crush. They don't like the fact that some individuals might have values and plans that differ from theirs, and rather than live and let live, they seek the political power to impose their plans upon all of us.
They believe that they have morality on their side. They believe that the individual must sacrifice for the community, that the rights of individuals can be subjugated to the "public good". But they are wrong--morality is not on their side. Life is not a battle over who will sacrifice and who will collect those sacrifices.
When confronted with the nature of their ideas the pro-planners have no rational response. When the principles they advocate are refuted they can only shout bromides. When their moral premises are challenged, they have no defense. And that is something they did not plan for.