Depends on how much you have failed.
If its a simple double lift that split, you can probably act surprised and continue. They'll probably forget about it soon enough
If its a major gimmick breaking apart, like... the igniter... then you should just apologize and continue, or make a joke out of it.
But you should just practice as much as possible and allow the only mistakes you make to be situational and pure fluke.
Its not always a bad thing either... sometimes it may bring the atmosphere down then back up. Its mostly experience which teaches you how to get over these things, but the first few times are surprisingly easy.
Just don't panic and you'll be fine. No one is going to hate you for messing up a trick.