I can't think of a single performer (of any sort) that's not botched their lines or an effect. Harry Blackstone has had the thread break when doing the Floating Light Bulb while others have had lousy technicians not following their cues and the result was flashing the wire form for the Asrah. . . the list is infinite!
In some fields of magic -- namely, Mentalism -- a miss can actually prove a thing of benefit. For the most part however a fouled effect can prove emotionally devastating. I did a set at the Magic Castle one evening in which every single effect in the 15 minute spot, FAILED!
The girl didn't get into her hide position when we introduced the Shadow Box and so when I opened to show the empty cabinet, she was already there. . . the Zig Zag started folding up because my tech didn't lock it for performance. . . the dove was dead. . . the spine to my Asrah was broken . . . it was hell!
The set following this catastrophe however, went smooth as silk as did all the successive presentations. . . and we'll not get into the issues one faces when working with animals; kids and animals are unpredictable and can cause you to develop ulcers.
I believe it was Billy McComb that did a lectured entitled "What If the String Breaks?" in which he explores the issue of failure and having OUTS. . . rehearsing for failure as it were and in the case of larger scaled shows, training your crew to think on their feet so that issues can be corrected during a performance. In short, doing Magic Tricks don't make you a "Magician", it's learning how to overcome "issues" during your performance, obfuscating the fact that something went array.
I'm all thumbs when it comes to working with IT and for this reason I have redundant hook-ups and alternative methods at the wait, should I have a mishap -- failure on one hook-up and so I can rely on the other, etc. It's not the easiest thing to do but it's how I learned to deal with one of my shortcomings and create a limited number of fail-safes. The moral of the story being, if you know that you have a weakness in a given area with a specific technique, plan for failure and create OUTS; Banachek mentions this in the opening of his Psychological Subtleties book (1) and for some unknown reason about 75% of the people that graze through the books seem to ignore his warning about how to use said method in order to protect yourself from likely failure. Then again, a lot of Mentalism, especially the newer material that is leaning heavily on the art of suggestion and hypnosis, comes with a known 15-25% failure rate, especially when you're first learning it.
Bottom line is, accidents, incidents, and general muck-ups happen; animals poop at the most inopportune moments, mirrors streak and lend a tattle tale (they likewise reflect spot lights). . . and the list goes on -- the show MUST go on, so as they say. . .
RULE ONE: Don't Sweat the Small Stuff
RULE TWO: When in Doubt, Refer to Rule #1
That's how it works