Others have highlighted it Galen, but I wonder if this feeling is to do with grieving. When we have a large grief it seems to highlight the smaller ones such as missed opportunities, decisions we regret, etc.
I said earlier on that I certainly feel like this quite a bit of the time and I do feel this is partly a mishmash of smaller griefs. Motivating yourself becomes difficult when this happens and I don't think it is at all surprising that you did not want to socialise, by the way.
I find the "two minute rule" helps although it would not work for everyone. If I am feeling I just cannot do anything I look at the thing I am wanting to do - anything from you doing a law course to the ironing - and I tell myself I can do two minutes of it. Sometimes that's all you can do, e.g., make a phone call to get details of a course, sometimes you can do more, but you will have done something.
Interestingly I find I am quite able to do the things involved in my mother's care. It is when the focus is just on me that it can be a problem. This may not help but hopefully knowing others feel as you do will. I know your OP helped me feel less alone with this.