In my Madoka Magica psychodrama, the part played by Sayaka Miki is of course central, and never more so than in her attitude to irrevocable decisions and regret. (No, this is not a post about Brexit.) Before she decides to become a magical girl she worries about regretting it later; having taken that step, the refusal to regret becomes for her a test of her own moral worth, and she constantly monitors herself for signs of it. It's a test she cannot possibly pass in the long run, of course. When the consequences become too painful for her to bear, she cuts herself off from her pain (using magic, but alcohol is an alternative).
I've been learning her signature theme, "Decretum", for some time now, and had hoped to upload a piano version of it before going to the hospital tomorrow, but it's not quite there. So, I'll have to make do with what for my money is the most painful of Sayaka's scenes, which features "Decretum" in full and, appropriately, much cutting off of heads.