Another interesting topic

. I think it depends how one defines luck, I don't believe in luck as any fatalistic special magical thing; the way in which I would define it is based on the things which one doesn't have any direct control over oneself. If the things one has no control over happen to go in one's favour, then that's 'good luck' and if they don't then it's 'bad luck'. Doesn't necessarily mean anything special is happening or someone or something is watching over and causing these effects, just that the events in the world must pan out in some way, whatever that may be, and the person will either be affected positively or negatively depending how this happens to occur. So when I wish someone good luck for an exam, I'm not believing that my saying of that will cause the uncontrollable things somehow to magically go in their favour, I'm simply wishing them well, in the sense of letting them know that I hope they will do well (not that I believe hoping will affect the outcome, but I'm sure most people will agree it's nice to feel people are thinking of them

).
I certainly think a lot is blamed on bad luck when it is really bad preparation. I don't think it's bad luck if nerves get the better of me and I'm unable to play, because I know that I will be nervous. Yes it's hard to predict when a piece can withstand that level of nerves and indeed what that level is, especially since it nerves at that level are unlikely to take effect until the day of the exam. However, it's not bad
luck per-sé because I will get nervous in the exam (to some extent, knowing me this will be a large extent and it will affect my playing) and if I prepare enough I will be able to play well in spite of this. Whether I have prepared enough when the time has come is not a matter of luck though, it's something that's happened in the past, how nervous I get isn't a matter of luck really: I will be nervous, so there's no luck in it, just a case of whether or not I have in the past done enough preparation. Of course it's natural human instinct to have come out of the exam, and played it right in every other situation, to still feel that I have been unlucky if it goes wrong then, but I haven't really I just hadn't prepared enough for the situation. There is an element of risk: not knowing how much the nerves will affect my playing, and of course, this is the skill in knowing when to enter and how much preparation to do, but it isn't luck.
Again to take someone else's example, if someone keeps me awake all the previous night, if I'm well prepared I'll do the playing well anyway, if my playing was shaky enough to be affected by that then it should have been better prepared in the first place so that risk wasn't there.
The effect of the elements that are beyond one's control are a lot smaller than those that are within one's control: someone who is destined to achieve 140 if they play as they normally do, isn't going to fail the exam because the examiner is mean, the piano isn't good, or they didn't sleep last night. Yes they may get 135 instead of 140 because of some of these factors (if the marks were lower I'd expect the fluctuation to be smaller, i.e. one may get 125 instead of 127, and around pass/merit/distinction boundaries, it's much harder to gain/lose marks). In summary, luck does affect things in the sense of uncontrollable factors going in someone's favour, and I suspect would cause small fluctuations in marks, but the difference one can make in terms of preparation and controllable factors overrides this greatly, to the point that these factors aren't nearly as important as is often said to be the case.