David, I am also a year into keto, 60 years old and very much in the groove with so many non scale victories that I can’t go back to the dark side. I have an 18/6 eating window too with no snacking at all. When I used to eat carbs I would have to have a nap in the afternoon but now it’s easy to power on through with lots of energy. I love coffee and have limited myself to just one strong one in the morning to get me going and one espresso 2-3 hours after my first meal which pulls me through easily to dinner. I have found that after my first meal if I ‘get busy’ with my cottage chores, painting, building, gardening, lawn maintenance … etc it really helps with the crash and burn. The get busy after eating not only keeps me going, energized and motivated but also gets stuff done. If I don’t feel like working, we go boating, fishing or goof off. I also weight lift/exercise 4-5 days a week now that I am in awesome Banting preservation mode which gives me a bunch more energy. So in short I would say, get motivated to get busy after your first feed and force yourself to exercise, get your energy levels up. It has worked well for me.
The afternoon espresso is a reward bonus. My problem is I don’t sleep anymore, I run on 5-6 hours since going to the LCHF diet