Even accepting such a tautological definition, this would depend on our ability to evaluate evidence impartially and without error and be able to cognitively file all of our beliefs/hypotheses/etc. correctly and make meaningful distinctions between them when informing actions.
I believe my wife loves me. I have lots of evidence that supports this. But then again, many others who felt the same found out they were wrong.
Not sure she'd be too chuffed if I told her that I can only consider it a working hypothesis that she loves me, because it wouldn;t be sufficiently rational to believe it
It can do, and to some extent, all of us are emotionally driven and blind ourselves to emotionally unappealing truths, or easily believe emotionally pleasing untruths.
Emotions are far more powerful than facts, and we rarely change that which we hold dear simply because it can be shown to be wrong (or highly implausible).
Some people no doubt do.
Personally, I found it more emotionally satisfying to believe in the post-Enlightenment myth that humans were rational and making progress, and that as people god richer and better educated they'd become more rational too. The idea of melioristic progress is quite reassuring after all, just as for many belief in God's love is.
The idea of melioristic progress through reason is just a remixed version of Divine Providence that emerged in Christianity then moved through Providential Deism into secular humanism.
It took me years to lose my faith in reason and reject secular humanism. Not because I wanted to believe in spirits or gods or flying saucers, but for the same reason some people lose faith in God: they can no longer justify believing that which they perceive as being contrary to the evidence.
It doesn't matter how much value one affords to reason, humans just aren't very rational in the overall scheme of things.
Of course, you will probably disagree with some of my opinions above, but whether it is right or wrong, my disbelief in human reason was not to protect an emotional need. It was more the opposite, cognitive dissonance made me reject much evidence for years.