It is unwise to let rationality dictate all of one's behavior. Certain behavior should be dictated instead by the effect it creates. The principle of karma is a useful example. Rationality tells you that karma as a magical force isn't real; rationality would dictate against practicing it as a behavior. Despite this being true and karma not being real, karma has positive effects on those who practice it, both individually and wider on a cultural or even societal level. It encourages moral behavior and discourages immoral behavior. So, karma should be practiced despite it being irrational because it has a positive effect. In this instance, and in many others, rationality should be rejected. This doesn't mean rationality as a whole should be abandoned. Rationality is an incredibly powerful tool but it's unwise to live by it universally.
This selective rejection of rationality goes both ways. Rationality can dictate behavior that creates a negative effect but is still followed because it's deemed as rational. In this example, rejecting karma as a magical principle is rational. However, rejecting it would also reject the potential positive effects it can have regardless of its irrationality. It's easy to become blind sighted when using rationality as a tool. In the pursuit of what is good and what is true it is just as vital to keep in mind what effect your behaviors are having on you.
Rationality tells us that the bible is false. However, the bibles ability to survive as a tradition for thousands of years is evident that practicing christianity has both individual positive effects as well as societal. If this isn't true then christianity wouldn't have survived as a tradition for so long.When questioning whether or not to uphold Judeo-Christian values, one shouldnt question the rationality of the stories behind these values, but rather the effect created by practicing and upholding them.