Come on people! Just put one foot in front of the other. Start doing something. If it's not working for you, change, optimize, tweak. You don't get into habit by planning on doing it for two months and then expect to the first day to go great and day 30 to look like day one. Some of the best days in the gym have been when I don't want to go, but I tell myself to go the the gym. And then I tell myself: "One more set." And then: "One more set." Before I know it, I've got a pretty good workout in.
Great book on habit: Charles Duhigg's 'The Power of Habit.'