a. an object of irrational reverence or obsessive devotion
b. a strong and unusual need or desire for something
In today's modern society (modern western society at least) we seem to fetishize consistency. We call politicians who change their minds on issues or change their views "flip-floppers." Who among us hasn't defended an opinion we no longer held simply because we held it before and discussed it with others? Both externally and internally in our own minds, we seem to have this unusual and intense desire to remain consistent with our past thoughts, beliefs, actions, words, and desires - we seem to have an irrational and unfounded fear of admitting that we've changed our minds on something or that we've grown up a bit and now see the parts of the picture that we didn't see before.
It's not clear where this fetishism of consistency comes from. It could arise from without (an external influence on us by the media or the education system) or it could arise organically from within (many individuals valuing consistency and see it as a vital trait). Regardless of where it comes from, today's intense devotion to consistency has likely gone too far - some consistency is important, BUT putting consistency above all else (including growth, education, and flexibility) is a foolish thing for a person to do and a foolish thing for a society to exalt.
If you believed X in the past but now believe Y, you must not be afraid to admit either to yourself or to others that your position has moved. Of course, if you consistently change positions or can never make up your mind on issues, that's a problem of its own, but when you move from X to Y because of personal growth, because of education on the topic, or because of an increased internal flexibility, you are acting in a very human and correct way.
In short, it's ok to change your mind when
But, your mind really hasn't changed if