I’m a solo practitioner, and was diagnosed just under two years ago. Welcome to the club. It’s a very large club.
If I had to guess as to the source of the guilt, I would say training. You have three decades of training in feeling bad about yourself, and feeling like your failings are moral ones. It takes more than a couple of weeks and some pills to overcome three decades of telling yourself “I’m failing because I’m a bad person.”
Even now, you are saying that whether or not you did something was based on whether it fell above or below your importance line, but also, ‘sometimes’ you couldn’t decide. Seriously consider the possibility that you were never really using importance to decide how to behave. Consider the possibility that it was some combination of interest, novelty, urgency, energy level, and anxiety that was deciding what you would do, and that you were just fortunate enough that those other factors worked out well until now.
You feel guilty because you have been trained to feel guilty. So now, even though it no longer makes sense to you, the feeling is still there. I say “still” because it probably always was. It just wasn’t something that got your attention before.
Don’t worry about that. That’s normal. It’s just an emotion. Feel it. Notice what it’s like. Notice what makes it go away.