A popular tautological observation often used to briefly distract us from the sad state of reality by reminding us how much more unpleasant the world would be if things were not what they are, leading to such terrifying consequences as square circles, married bachelors, and depressing happiness. Other popular tautologies include the following:
Kids will be kids.
Not entirely correct, since kids are kids right now and they will stop being kids once they reach the age of majority. Still, adults can rest assured knowing that kids, never having been adults, are much worse at being adults than adults (who according to rumor were kids once) are at being kids, which means that they don't run the danger of becoming obsolete any time soon, especially due to the built-in feature that turns kids into adults without fail.
Just be yourself.
A rare breed of command that is impossible to disobey, much like "listen to what I'm saying to you" and "look what you've done". Being anybody else but yourself is somewhat tricky since you'd be them, but they'd be you, meaning that by the transitive property, you'd be you. This is fortunate, however, because, given that most people aren't very good at being themselves, one can only imagine how badly they would do at being someone else, if only out of spite to make themselves look better.
Everyone has their right to their opinion.
A corollary of this is that people don't have the right to other people's opinions, which is good, because most people could not resist the temptation to fine-tune everyone else's opinions to their own. An entire planet of people sharing your nuanced opinions on consumerism, the role of the state in human affairs, and the writings of James Joyce would mean a lifetime of preaching to the choir, and everyone secretly enjoys disagreeing with others, even if some people would disagree with that last statement.
Rules are rules.
An interesting self-referential tautology, as it is arguably a rule itself. One can only wonder how unpleasant the world would be if common sense rules such as "be nice", "respect others", and "don't do to others what you don't want done to you" weren't hard-and-fast rules that everyone knows to obey for the common good, but mere suggestions that could be modified, ignored, or circumvented as potential personal gain dictates.
It will be finished when it's finished.
This observation rests on the well-accepted rule of reality that the same event cannot happen at different times, unless that event involves a mistaken decision.