Habit change requires 85% of your total energy upfront, just like a space shuttle needs booster rockets that comprise 85% of the total weight to achieve escape velocity from Earth's gravity

Space shuttles are strapped to giant booster rockets that are '85% of the weight of the two of them together' and fire for 'just a couple of minutes' to launch the shuttle '26 miles into the atmosphere' to achieve escape velocity, after which 'those little rockets on the back can fire for the next couple of weeks'