Right now my most immediate one is re-learning cooking for one.
I know there's frozen/prepared, but I prefer things done from scratch. It's also a good way to keep the excess salt problem under reasonable control. What I've found that works for me is one major cooking session about once a week, dividing the results, and freezing them as one at a time portions.
[During the week my microwave is my friend.]
Last night I did both a meatloaf and meat balls. In about two and a half hours I now have the protein component done for approximately two weeks worth of meals. My cost, even with spices was less than $11.00 in total. I'd previously done chicken, and have a supply of both fish and chops. I vary things from night to night of course.
Salads are quick, and so are some other veggies. Potatoes are a problem - I don't really like instant and "from scratch" takes a while. Pasta is quick enough and rice is not too bad.
The biggest problem that I've encountered is buying for one, especially fresh vegetables. There are some things that I like, but not every day. Carrots keep, but greens are problematic.
I'll figure it out.