I reckon there's three key things to keeping a good regular commute going.
Good sleep, good energy levels (from food) & dedicated mindset.
Im averaging about 70 miles a day at the minute and I couldn't do that without getting some decent sleep and taking in a lot of energy. Take today's food intake so far. Brekkie at home @ 05:00am consisted of 80g's of porridge made with 300ml milk, sultanas, a banana and strawberry jam. I had a 32 mile ride in this morning then had a 2nd brekkie at work which was 4 brown toast, 4 poached eggs, beans, 2 fried bread and 2 cups of tea. I've just finished my lunch of 3 tuna sandwiches, two kitkats, a Yorkie, a whole malt loaf, 2 bags of Haribo and a half pack of jelly babies. I've got a flapjack and another Yorkie for 14:30pm ready for 15:00 ride time where I'm thinking of a 60/70 miler.
Consistency is key though, day in, day out, day in, day out, again, again, again.