I'm going to copy/paste and paraphrase something I already wrote.. because I still stand by a lot of it..
To me, Regret is a necessary poison.. like terrible tasting medicine that you need to take for a while. It feels and tastes horrible... but somehow you know that someone, with your best interests in mind, made this concoction for you to ease the pain...
I believe God ( or whatever you believe in ) allows regret to envelope us sometimes to help shape the future....a form of personal inner therapy... it's a necessary tool... it's a sign.. it's a signal... it's his voice saying "it's ok to feel this way... it's ok to feel... " .. it's a way of filtering out the noise and making sense of everything ... it forces us to ask Why? even when there is no answer... in the end we're beings with free will.. we can allow ourselves to only feel regret and never, as you say, lift ourselves out of the fog. That's where it gets incredibly tough... incredibly daunting... .like it's impossible to see through the thick... but ... just know that it is possible.. there is a clear sky past that thick veil of fog. Time heals... you heal... it's all part of the impossibly painful process that we've all been through.
I didn't think I'd survive losing both my parents to cancer... both died in the same room in Palliative care, 14 years apart ... that impossibilty paralyzed me for a time... but when I started focusing on what I did do for them rather than all of the millions of things Icould have done for them.. it started getting easier.
On the way to work the day I originally wrote this, I had flashed back to a month before my mother died... days before she went into palliative care... I was visiting her here and there at her home.. but in the evenings I was... I .. was... working on my WEBSITE!!! oh my... that burned me... that destroyed me when I realized afterwards I had been spending hours deciding on fonts and colors and pictures for my website rather than discussing life, and love, and everything in between with my mother by her side... but does that change anything now? Can I go back and change that? no.. so why focus needless energy on that.. I regretted it... I admitted it.. I felt it... I let it go.. it is what it is...
but when I think about the time i DID spend with her.. the time I brought her a coffee and donut from the local coffee shop and saw her eyes light up... she had half a bite and only a sip but it made her smile .. made her day.
focus on those memories.. yes, let the regret do its thing, ..but remember... you're in control even when it doesn't feel that way.