When people think of broken New Year’s resolutions, ones that may not have even lasted a month, one of the first things that often comes to mind is "this year, I’m going to get more exercise." Gyms often waive their initiation fees for the first two weeks of January, or the entire month, to draw in eager new exercisers—and more than make it back when people who joined in the first wave of enthusiasm continue the membership without actually ever going. Resolutions often fail, but exercise seems to be particularly—or perhaps just publicly—difficult for people to stick to.
So why do people who are initially determined not to go to the gym end up not doing so? One part of it is that exercise is boring. People generally understand that actually putting in the work to exercise is needed to see results, but when they are looking at it prospectively people tend to overestimate their determination to go to the gym, overestimate their self-discipline, and underestimate the tedium of actually exercising. In particular, what is called "impact bias," a feature of how the mind works, causes people to overestimate how strongly and for how long they will maintain the future intention to go to the gym on a regular basis. When it comes to feel like a chore, people are motivated to dodge it.
That’s why experts recommend starting slowly and building up. Many people start out intending to go every day, in order to see results as soon as possible, in the hopes of developing a habit, and in an effort to remind themselves how serious they are about this. Unfortunately, an intense workout every day is likely to backfire. For a beginner, this can quickly become overwhelming, and seem like an impossible task. It also becomes tiresome sooner, as opposed to a once or twice a week gym night or morning being something to look forward to and savor the anticipation of. Four or five workouts a day may be possible in the long run—though every day is probably a bit excessive for most people—but it’s too much right from the outset.