Why do habits created for healthy eating and exercise often fail when real life gets in the way? originally appeared on Quora, the place to gain and share knowledge, empowering people to learn from others and better understand the world.

A lot of very popular books tout forming automatic habits as a path to success for virtually everything. And I have to admit, the idea of putting all of our decision-making on autopilot is very attractive. Making fewer decisions seems so much easier! But I also have to say that for most people, forming automatic habits for eating and exercise just doesn’t work. There are two significant reasons why.

First, habit formation is based on the three-part habit loop: cue, behavior, reward. This works wonderfully for simple behaviors like remembering to floss your teeth after you brush. Brushing your teeth is the cue for the behavior, flossing is the behavior, and your reward is the pleasing feeling of clean teeth and sense of accomplishment before bedtime. This works well because it happens, in the same way, every day: in the evening, before bedtime, and after you brush your teeth. If you’re already in the brushing habit, tacking flossing on to the activity is pretty easy.

Successfully forming and maintaining an automatic habit necessitates that the habit loop stay the same, with unwavering components and circumstances. And let’s face it, there’s not a lot of hubbub in the bathroom that could disrupt this habit loop. (Most of the time!) And (again, most of the time!) we don’t spend the whole day in the bathroom.

Yet for many of us, daily life is the opposite of the predictable routines we perform alone in the bathroom. It’s full of the many people we care about, often chaotic and noisy, and full of disruption! No matter how much we may try to streamline our lives or make detailed plans, the more likely scenario is that something unexpected occurs that upsets the program, including our schedules and eating and exercise plans.

Add to this busy, distracting, constantly changing life context, trying to form automatic habits for complex behaviors like eating and exercise. The task of keeping an identical workout or healthy eating cue within your busy days is more than daunting – it’s nearly impossible for many of us. When our intentional eating or exercise plans bump up against real-life—especially if we are not habiters, or able to rely on outside support—they are likely to crash and burn, taking down their habit loop in the process.

The second reason it’s hard to form automatic habits for healthy eating and exercise has to do with the reward component of the loop, specifically how our emotional relationships with these behaviors influence our feelings toward doing them.

We know from research and from past personal experience that changing our eating and exercise behaviors is different from changing other behaviors. That’s because both eating and exercise are uniquely intertwined with the challenge of losing weight and the psychic heaviness this goal is so often accompanied by. This means that eating and exercise are also inextricably connected to our numerous past negative experiences, such as embarrassment in PE and shame in the doctor’s office, and to other negative emotions such as self-conscious and perceived failure.

Our brain tags these memories as negative, enticing us to avoid the very choice we had planned or approach the one we had hoped to avoid. This phenomenon doesn’t just contaminate our motivation for exercising and healthier eating, it thwarts the very reward needed to continuously drive the habit loop.

When we understand the assumptions underlying habit formation, it’s easy to see why it can’t work for the many of us who have complex daily lives or complex relationships with eating and exercise.

This question originally appeared on Quora.

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