Rationalization is about making excuses. It is about justifying our behaviors after the fact, interpreting the situation for our own benefit.
We all do it. It allows us mental freedom to put in less effort into our endeavors by freeing us from taking responsibility for our actions. By freeing us from personal responsibility, we don’t have to worry about correcting our own behavior. We can pin the problem on others, we can say some situation was the reason for our problems.
From an evolutionary perspective it makes sense. By conserving the energy that would take to assume responsibility and improve ourselves or fix the situation, we can focus that energy on survival as survival was the main goal in our ancestors’ time. It allows us to conserve energy without expending efforts on the wrong things.
However, nowadays the issue is different. For the most of us, survival is close to guaranteed. We can expend our efforts in improving ourselves and fixing problems and not worry about how to survive. So does rationalization make sense in the modern era? Most likely not. It is almost completely worth it to assume the responsibility for behaviors and not making excuses. It helps us become a better person whether or not the excuses are valid.