When the guilt came back
It will. A bad week, a fall, a hospital stay, a sibling remark, and the amount goes out of the window and you're doing everything again, and the should is running the visits, and you notice on the drive home that the second guilt is back.
The first thing to know is that a fortnight of penance doesn't undo the decision. The decision was a sentence, chapter 23, and a sentence can be said again. A crisis needs more care, and more care given on purpose for a crisis is chosen care. Going every day during the hospital stay is not a lapse. Still going every day a month after she's home, without having decided to, is drift, and the fix for drift is to sit down and write the amount again.
The second is what to do with the guilt about the lapse itself. You'll feel it, because you always did, and there's a temptation to make it up with a penance visit, which is the loop from chapter 14. Don't. Gonyea's daughters were told by their own researchers that the standards need revising, not meeting. The way back is not another visit. It's the amount, said out loud, this Sunday.
The third is to ask which belief let the guilt back in. It's usually one of the chapters. Nobody else could do it properly during the crisis, chapter 11, and now you can't hand it back. She's expecting it now, chapter 16, because a month of daily visits reset her expectation and you didn't say the amount when things settled. Your brother did nothing again, chapter 8, and the sums came back with him. Find the belief, reread the chapter, and say the amount.
And be plain with yourself that some lapses are a sign the amount was wrong. If you keep drifting up, maybe you want to give more, and you can, on purpose. If you keep drifting into resentment, the amount was too high, or the help in hasn't happened. The lapse is information, chapter 14 again. It isn't proof that you're the daughter who couldn't keep it up. It's a message about the arrangement, and arrangements can be changed.