productivity

The most important (and possibly the hardest) exam of my life is in 3 weeks. I am looking for a good balance between:
* sleeping
* eating
* stimulants
* focused work
* exercise/yoga/etc
* leisure

... more specifically a daily schedule for the above. (Should "leisure" be absent?)

A good 20 minutes of cardio seems to make everything easier, but: when I am productive, I don't want to take breaks; and when I'm not productive, it's even harder to justify it to myself. I guess stimulants help me stay on task, but the effect is not big enough to be obviously better than placebo, and they can make me wake up too early the next day.

It would be nice if there were an atheist version of prayer.