I don't know how Christianity is supposed to work in therms of guilt. I have felt the big internalized guilt thing, but dropped it (mostly) more out of pragmatism than for any other reason. I observed that the more horrible I felt about doing or failing to do something, the more inclined I am to do it. Maybe it's effective for some people. For me it is paralyzing and/or compelling in a bad way. It took some effort to learn how to shut it down or at least mute it some, but I do much better with it than I did.
I see little value in crying over spilled milk, so to speak. Like you, what matters to me is what happens next. You can't change the past, so why dwell on it except for the purpose of learning and doing better next time?
It's not a huge number of options, but it's more than nothing. I cannot choose how certain things make me feel, but I can choose, to some degree what I let myself be exposed to and what I will think about. I choose who I actively allow to press my buttons. I choose to press or not to press certain buttons on others. The conscious choices I make about these things are my own and my self. By choosing those things, I choose my feelings and that makes them my own.