When people perform from memory they are often worried that they might have a memory lapse (forget how the music goes). It can happen, of course, even to the greatest musicians. The famous violinist Bronislaw Huberman and the pianist Eugen d’Albert were once performing Beethoven’s "Kreutzer Sonata". Both were playing from memory. One of them kept going wrong in the same place, playing something that had happened earlier, so that they played the middle bit three times before eventually managing to finish the piece. However, this is quite common, and can happen to anyone. 