When you told me that you have tried meditation, i didn't liked the idea. meditation is good but what you were called meditation did sounded like an unnecessary ritual which (i believed) will lead to more confusion rather than calm your mind and make you realize some fundamental truth about yourself.
but now i read your lines:

I realized that if I wanted to make any progress, I needed to stop obsessing with guilt and regret and simply be the best possible human I can be, with every day I have to live. "one day at a time" as it were

i'm very happy that you find that out with or without meditation, that is what matters the most. there is no past or future because there is only now. there was now in the past and there will be a now in the future when it's time. therefore all we should worry about is now.

i'm very happy to know you and glad being your friend. good luck with your projects! :)