The idea of a keystone habit (from Charles Duhigg's The Power of Habit) is that some habits drag a whole load of others along behind them. Start exercising regularly and people often find they eat better, sleep more and procrastinate less — not because they planned to, but because the one habit reset the tone. Find your keystone and you get a lot of leverage from a single change.
The trick is picking the right one and actually keeping it — which is where tracking earns its place. This tool lets you mark a habit as your keystone (it calls it your core habit) and hold yourself to it daily, so you can watch whether it really does pull the others up. Just try it: pick the one habit you suspect changes everything else, and track it for a month.