The treat that became the habit
What the guilt is doing
Most people with a daily have a bit of guilt about it, and most of them think of the guilt as the price. The treat is the pleasure, the guilt is what it costs, and on the whole it's worth it. I'd like to suggest the guilt is part of the pleasure, and that this is why the daily is hard to shift.
Kelly Goldsmith, Eunice Kim Cho and Ravi Dhar found that activating guilt in people made the pleasure they got from a pleasant thing greater, not smaller. Their explanation is that guilt and pleasure are associated in the mind, so that switching one on switches on thoughts of the other, and they found the effect was particular to guilt. Other negative feelings didn't do it. It's a marketing study and the pleasant things were the kind you'd expect, but the finding matches something you can check in your own kitchen. The treat that's a little bit naughty is nicer than the same thing eaten with a clear conscience. The word "naughty" is doing work on the label of every pudding in the shop for a reason.
So the guilt isn't the price. It's a flavour. And a flavour is a hard thing to give up, because you can't reason it away. If you managed to feel no guilt at all about the glass at six, my guess is that the glass would be less nice, not more, and that's a useful thing to know before you try either of the two ways out in chapter 18. Dropping the earning, which is one of the ways, means dropping the guilt the earning was there to pay for, and the treat may get a little duller. That's not a failure. That's what it tastes like on its own.
The second helping of guilt is the one at bedtime, and it works the other way. The daily leaves a small bad feeling at the end of the evening, another glass, another bar, another hour gone, and the bad feeling is uncomfortable, and tomorrow at six there's a thing that's good at making uncomfortable feelings go quiet. The guilt from last night's treat is part of what tomorrow's is for. I can't show you a study of that loop, and it's my reading. But if it's right, then the guilt is holding the daily up from both ends, and the thing to do with it isn't to feel more of it. It's to stop treating it as information about your character and start treating it as a flavour you can do without.