The thoughts that enter a person’s consciousness over a period of months, years and decades will have a determinative effect on the character of that person and the quality of life he or she experiences. In other words, what a person thinks about will largely determine the kind of person he or she becomes.

If this is true (and, as far as I know, no one denies it), what a person thinks about is one of the most important things about him or her. The choice to allow a train of thought to travel through one’s mind or to set a train of thought in motion is made countless times each day and is, therefore, common. Yet, precisely because that choice is made countless times a day, it determines one’s identity and is, therefore, critical.

It is vital for health and wellbeing that a person take control of, and responsibility for, his or her own thoughts. Yet many people do not know this is even possible. They are under the impression that thoughts originate outside themselves and, as such, are uncontrollable. They go wherever the most recent impulse takes them: into a success or revenge fantasy, or a replay of yesterday’s argument at work, or last night’s “Survivor’ episode. They don’t realize they are responsible for their thoughts and in control of them. That’s one thought that never enters their minds.

The moment one accepts responsibility for his or her thoughts is one of the most important moments in a person’s life. It makes positive change possible. It resets the future. It sets the stage for personal and spiritual growth.

Many people allow thoughts to run unsupervised through their minds. Those thoughts link together into a train of thought – often a runaway train – and they feel helpless to stop it. But people can, and must, take control of the trains of thought that pass through their minds. They have the power to refuse them admittance, direct them when they are admitted, and stop them when they are going in the wrong direction.

A different analogy might be helpful. Imagine that thoughts travel along something like riverways or canals. The riverways – or neural pathways – are already in place by the time a person is mature enough to exercise control over them. Yet it is possible to redirect riverbeds or dig new canals – neural pathways – upon which one’s thoughts can travel. It is possible, but it takes significant effort.

One of the great engineering feats in U. S. history was the redirection of the Chicago River. In the early part of the twentieth century, it flowed into Lake Michigan, which provided Chicago with drinking water. Because the river was contaminated with human and industrial waste, drinking water was polluted, and tens of thousands of people died from typhoid, cholera, and dysentery.

The flow of the river was reversed by digging a system of canals, channeled through large sewage treatment plants, then into the Des Plaines River, the Mississippi, and eventually the Gulf of Mexico.

Something similar happens with us. Significant amounts of toxic thoughts are being dumped into our minds on a regular basis. We must prevent such thoughts from entering our stream of consciousness and polluting our minds. This means governing what we watch, read, and hear. TV, movies, books, and Facebook pages that continually dump toxic ideas must be shut off.

Even if we do this, some toxic thinking will remain, and more will enter our minds unbidden. So, we must take control of the thoughts we already have and redirect them. One way of doing this – a sewage treatment plant of sorts – is to routinely confess to God (and, as appropriate, to another person) toxic thoughts of pride, vengeance, fear, and sexual immorality.

Carving new riverbeds through which our thoughts can flow takes almost constant vigilance at first. It requires the painful work of confession. It depends on finding sources of clean and healthy thoughts: books, movies, websites, and people who introduce true and refreshing ideas to the mind. But as this hard work is done, the control of one’s thoughts becomes more manageable and life becomes healthier and more enjoyable.

Shayne Looper is the pastor of Lockwood Community Church in Branch County, Michigan. Read more at shaynelooper.com.