SOPP565: I practise every day for at least two hours and my latest piece is BWV 538

This question was sent by Allen. And he writes, Hi Vidas and Ausra, It is great to read other people's problems and challenges and I would love to hear your responses to mine. I took up the organ seriously in 2015 after retiring and I am now 71. I practise every day for at least two hours and my latest piece (which I have just mastered) is the Bach Toccata BWV 538 (Dorian). Unfortunately, I do have the occasional BAD day when everything goes wrong, even bars that never went wrong before. I soldier on but it often gets worse. Do you ever experience this? If so, what do you do? Hoping to hear from you, Allen