Guilt is a complex emotion and often goes hand in hand with shame, but can be mutually exclusive. Often it is our inner critic that causes those emotions which are sometimes warranted but sometimes not. An analogy is that 40ish years ago, I could buy codeine (highly addictive opioid), Valium (highly addictive benzodiazepine) and sudefadrene (used to make meth) over the counter at the chemist. Should the pharmacist feel guilt that he sold them to me or ashamed of himself for giving me such dangerous medication. Of course not, because at the time we didn’t know what we didn’t know. Years of biomedical research has brought to light the dangers of those classes of medication and restrictions are in place. If a pharmacist gave you a restricted class of medication now without a script, they should feel guilt and/or shame.
When you had that student, you didn’t know what you didn’t know, so your method was what you did know and, I assume, had brought success for other students so the brain has reinforced that behaviour over time. I haven’t been doing this course for long but it is diametrically opposed to the way I was taught. What I am assuming is that you have used a method that has worked for you, for other students, just not for this returning player. There is no reason for guilt that the chap gave up or shame that you might have failed him because, like the medication, the biomedical research had not been done.