No, you shouldn’t feel guilty! I just see it as extra food for another meal, as long as I am not throwing it away; no harm done. It is not my fault, I am not married. It would be different if I was cooking for one and I was married...then, I should feel guilty if I wasn’t feeding the husband.
I can eat at a fastfood restaurant alone, but not at one that you get waited on for every part of a meal. I feel self conscious eating at those places by myself...