On the other hand, too much symmetry is actually a bad thing, and just as symmetries are important it is the imperfections that drive real change and progress. As a mundane example I refer to the ratio of fifths earlier, not 2:3 but 2.0022:3. Also, you might note that faces are rarely if ever perfectly symmetric; while the most beautiful faces are probably fairly close, equally it's important that they aren't exactly reflections one half of the other, and as you snap into perfect symmetry faces tend to look, if not always awful, then certainly a bit off. It is the subtle imperfections that differentiate between beauty, or at least humanity, and some sort of artificial construction that can just look awful.
At a more fundamental level, the asymmetries or broken (ie almost-but-not-quite) symmetries turn out to be vital for getting everything rolling. As a physicist I'm going to quote a set of physics examples: I'd recommend reading further into these, if you get the chance (and aren't too exhausted by reading these already quite lengthy posts).
The first example is the asymmetry between matter and antimatter, still not completely understood. It the two were perfectly symmetric version of each other, then it follows that if you start with, say, equal quantities of matter and antimatter in the universe, then after a certain amount of time there would still be equal quantities of matter and antimatter, meeting and annihilating, and just generally messing up much hope of things just being stable. But we don't see this, and for whatever reason matter/ antimatter isn't a perfect symmetry. But because of that, here we are to moan about it.
As a second example, the Higgs boson is really just a manifestation of another symmetry that we should all be bloody grateful isn't perfect after all. This is the "electroweak" symmetry, that holds that two of the four currently known forces are really the same. Except that, if they were *exactly* the same, then nothing could have a mass (for various technical reasons, including Noether's theorem again). We have a mass, but this theory also works stupidly well at describing things. To reconcile the two is one of the more insane pieces of mathematical physics -- and, arguably, we still haven't reconciled it properly yet -- but it is doable and ends up implying both the importance of a symmetry and the occasional necessity for destroying that "perfection".
The third example I will give is in the currently completely theoretical concept of a Grand Unified Theory (GUT). These take various forms and, so far, they are all wrong. You might wonder, then, what motivated physicists to try them, then, and the answer, ironically enough, is an obsession with imposing as much symmetry as possible.
At this point in a typical particle physics lecture, your speaker would moan a lot about the unsolved problems of physics, and how "ugly" the Standard Model is, and bla bla bla. The GUT approach is to take the already fairly tightly-packed symmetries present, squeeze them into an consolidated symmetry, and then voila everything is perfect at last! Or not. In this case, the problem is that unifying symmetries has the unfortunate consequence of mixing things together that are observed to be separate. In particular, a proton can decay into an electron (+other)), but protons are stable particles with an observed lifetime of approximately 100 million trillion times longer than the age of the Universe, and the only way to fix this problem is to basically screw around with the theory until it stops being actually useful. Too much symmetry, then, is a bad thing just as much as too little symmetry can be.
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So in summary, then (I really don't want a third post), beauty, in the form of symmetry, is necessary for existence (not ours, per se, but of anything) but too much symmetry is bad for you. It's too constraining. Sometimes, it is the ugly stuff that makes the world go round.