Those who cheat once have a very high probability of doing so again says a study

We often hear that those who cheat once are more likely to do it again. As a matter of fact, this common belief also appears to be validated by scientific research.

Some studies have, indeed, confirmed that there is a tendency to repeat certain behaviors once certain "rules" have been broken and allowed social and personal taboos to practically disappear.

The secret seems to be in a region of the brain called the amygdala, responsible for emotional responses and therefore for feelings of guilt.

via bustle.com

When we lie or transgress with other people outside of an established love relationship, we initially feel bad, but when we repeat the same action, over time the psychophysical response will become weaker and weaker. In practice, it is a question of habit, in which one adapts and makes normal something that at the beginning was perceived as being wrong. 

There is no single reason that triggers infidelity, and in most cases, there are multiple concomitant factors. Some individuals are constantly suspended in a state of dissatisfaction, a condition that prevents them from being satisfied regardless of the situation in which they find themselves.

Such a person is unfaithful because something is missing in their relationship with their partner, but they still prefer to keep the relationship alive because contemporaneously, they are afraid of being left alone. To end a bad or meaningless relationship would, nevertheless, mean facing the reality of not having anyone, of being without a "safety net". 

The limbo in which liars and cheaters live is characterized by a lack of control over their emotions, mixed with a terror of true freedom. However, this situation is highly destructive not only for others but also for oneself as peace and equilibrium can never be found.

When you find yourself in this toxic loop, in this vicious circle of lies, deceptions, and denials, you have to stop and think and face reality. Repeating similar behaviors may seem gratifying in the short term but in the long run, it is useless as well as harmful.

First, you need to understand what is wrong with your relationship and eventually accept the truth when it is clear that it is time to end it.

Secondly, you need to understand what you are really looking for. If you are not ready for a serious relationship it is better to admit this to yourself and take personal responsibility for having chosen to remain alone.