A better way to phrase it would have been: "You cannot bend reality to your will simply by denying that it is what it is at the moment." (c.f. the manager who

A better way to phrase it would have been: "You cannot bend reality to your will simply by denying that it is what it is at the moment." (c.f. the manager who bellowed "I will not accept this forecast!") But that's not nearly as catchy a slogan as "you can't fight reality" notwithstanding that the latter is, as you point out, a vacuous tautology. For better or worse, part of current reality is that people are more attracted to catchy slogans than to nuanced truths, and so choosing to use the slogan is actually an example of employing the underlying advice.