Setting a theme for each month is an awesome idea!
Yes, I track these habits. There's an awesome app called TracknShare, super convenient. Here's how my list looks like:
http://imgur.com/I9qK9iu
I measure writing by the number of words I write each day, and I measure CS in "Pomodoros"(from pomodoro technique, 20-minute-sized chunks of uninterrupted time).
Participating in /r/WritingPrompts really helps with daily writing. Prompts are a great place to start, and provide instant gratification, also it's really fun.
When I have an interesting and exciting project to work on - I can easily stay on top of CS, but if not it becomes super hard.
The main thing about healthy food - is just throwing away everything unhealthy, and replacing it wih a lot of delicious healthy alternatives. If I get hungry and I don't have some nuts/berries to chew on immediately - I know I will go and buy chocolate/pizza. So it's mostly about controlling my environment. If everything around me is healthy - it's not that hard to keep it up.
When it comes to coffee and reddit - I still haven't found a good solution, I'm addicted to that stuff.
Exercising isn't that hard to keep up, just set a goal that is easy enough to not be intimidating, and spend several days paying attention to it, because when I don't I simply forget.