Have you ever evaluated and revised your existing beliefs? You might believe some things simply because they allow your bad habits (this might be unconscious on your part).
According to one of the most useful and widely-used theories in psychology — ‘cognitive dissonance’ — we tend to form beliefs that are convenient for us because such beliefs resolve our cognitive dissonance, a mental discomfort we feel when our actions are not consistent with our values and beliefs.
This is also called ‘rationalization’. By rationalizing, we selectively find arguments that justify our actions or habits, even when a counter-argument is more objectively convincing (which we choose to ignore or dismiss by further rationalization).
A good example is the belief in ‘karma’ — the belief that people bear the consequences of their actions in a previous life. Therefore, a poor person deserves to be poor because of their misdeeds in a past life. This belief frees a rich person from the need to help the poor. Their suffering is justified, they believe, and so is the lack of help. A belief in a wise god or creator may act in much the same way — ‘we should not mess with god’s natural order of things.’
Another example is the belief that ‘the world is a bad place’. It goes like this: the world is a rough place with many bad people and therefore, if you are nice and kind, you will be taken advantage of. This then justifies bad behavior or at least the lack of kindness. However, it can very easily be argued with plenty of evidence that the world is a good place with generally good people.
Another example is the belief that ‘greed is good’. According to this belief, by being greedy one will work hard and help grow the economy, thus benefiting the society. Of course, the economy can grow just as much or even more when there is collaboration and helping — plenty of evidence here too. Either way, greedy people are surely not being greedy for the good of the society! It is a rationalization that eliminates their mental discomfort (guilt, etc.) that would otherwise be too strong to ignore.
Similarly, cognitive dissonance and rationalization applies to many beliefs that we hold. Of course, one can choose to ignore one’s convenient but faulty beliefs, again rationalizing that ‘nobody’s perfect’. It is very difficult to give up convenience, pleasure, and comfort and even more difficult to put in the effort to change for the better. But if one does recognize by being self-aware that some held beliefs are indeed there to aid bad habits and actions, it will be an opportunity to grow as a human being. Humans can indeed evolve in one lifetime.