We are more likely to repeat a behavior when the experience is satisfying. Pleasure teaches your brain that a behavior is worth remembering and repeating. The story of chewing gum is paradigmatic. Chewing gum had been sold commercially throughout the 1800s, but it was not until Wrigley launched in 1891 that it became a worldwide habit. Early versions were made from relatively bland resins, chewy but not tasty. Wrigley revolutionized the industry, by adding flavors like peppermint and juicy fruits, which made the product flavorful and satisfying to use. Consumption skyrocketed and Wrigley became the largest chewing gum company in the world. 

Being a dentist, I can say the same for toothpaste. Toothpaste does not add any direct benefit to the teeth (nay in some cases it can cause damages). But owing to the tasty and smelly properties, it makes toothbrushing a pleasant experience with a final feeling of a clean mouth. This is going to reinforce the habit. 

What is rewarded is repeated. What is punished is avoided. 

The central issue is that we look for IMMEDIATE SATISFACTION. Our brain has been evolving in the savannah for hundreds of thousands of years, where you are constantly focused on the present or near future. The scientists call it an immediate-return environment, where your actions instantly deliver clear and immediate outcomes. In Savannah we were in a hurry. 

Now, we, homo sapiens, have been living, for a thousand of years, in a society into which many of the choices you make today will not benefit you immediately. If you do a good job at work, you’ll get a paycheck in a few weeks. If you save money, you will benefit decades later. You live now in a delayed -return environment, because you can work for years before your actions deliver the intended payoff. 

But we are walking around with the same paleolithic hardware of our ancestors living in the savannah. 

Compared to the age of the brain, modern society is brand-new. And whilst in savannah it made sense to focus on instant gratification (because the distant future was less of concern), in modern society it would make more sense to focus on long-term gratification. 

Why would someone smoke if they know it increases the risk of lung cancer? Why would someone overeat when they know it increases the risk of obesity? Why would someone have unsafe sex in they know it can result in sexually trasmitteded disease? 

Once you understand how brains prioritize rewards, the answers become clear: the consequences of bad habits are delayed while the rewards are immediate. Smoking might kill you in ten years, but reduces stress and easing nicotine craving NOW. Overeating is harmful in the long run, but appetizing in the MOMENT. Sex provides pleasure RIGHT AWAY. Diseases and infection will not show up for weeks or years. 

The French economist Frédéric Bastiat explained the problem clearly when he wrote  “It almost always happens that when the immediate consequences are favorable, the later consequences are disastrous, and vice versa. Often the sweeter the first fruit of a habit, the more bitter are its later fruits’‘.

According to the Naval’s Razor (from Naval Ravikant) if you can’t decide between 2 choices, take the path that’s more difficult/painful in the short term. Doing this will counteract “hyperbolic discounting,” the brain’s tendency to overestimate short term pain and underestimate long term pain.

We perceive objects in time similarly to how we perceive objects through space. The further something is away in space, the smaller is appears. The same is also true of time: the further something is into the future, the smaller is perceived by our brain (the same is for the past). Thus, we tend to underestimate the problems and rewards in the future, and overestimate problems and rewards in the present, leading us to a “shor-termist” approach in decision-making. We perceive that what happens now is more important than what will happen in the future. And this is also the reason of our tendency to procrastinate.

You should strive to remember that your brain is rooted and configured to make you overestimate the present and underestimate the future. According to the mathematician Carl Gustav Jacob Jacobi “Invert, always Invert”.