Normally I'm in school and I cook very simple things 2-3 times a week. However, in the summer when I'm working full-time (such as now) I am exhausted when I get home and cooking is the last thing I want to do. I try to cook on Sunday nights during summer. I really do enjoy cooking, but cooking for one is tedious and I hate the cleanup afterwards.
Luckily this summer I get taken out to lunch a lot and they are often large and long so I'm not really hungry in the evening. A protein shake at that point does the trick for the most part. If I actually want a real meal, I might grab something from the freezer or hit up Subway/Togo's/Quizno's/Chinese/Thai takeout