I'm bipolar and was very sick for years, which lead me to do a huge amount of things I could regret. I don't see any point in regretting though, what's done is done and there's no way to change it. I sometimes get stuck in thinking about the horrible things I've done and what I put myself through, and then I turn my mind around by doing a mindfulness exercise or something. There's no way to look than forward. Looking in the rear view mirror won't get me anywhere.
Not taking care of myself first. Very hard lesson.
1.) I would say to unplug and take some time each day to reflect on the purpose for which you have been created. So many people are miserable because they are not fulfilling the purpose for which they were created.
2.) I regret not living life to fulfill my purpose. I instead tried to assimilate into the environment around me.