Forgot a Chore

I'm starting my first year of law school this fall, but I also take care of my partner, who's in her twenties. We have our routines and rules, and usually, I enjoy following them. This week, though, I felt so overwhelmed with assignments that I forgot to do one of the chores she asked me to handle. She trusted me with it, and now I'm feeling really guilty about breaking my promise. It's not a big deal in the grand scheme of things, but I know how much little actions can affect our trust, especially when we're both dealing with heavy loads at school and work. I just want to make sure she knows how sorry I am.