Thriftiness is like fitness - it requires both a healthy diet and exercise. In thriftiness' case, this means spending on things of good value and accruing wealth (that sounds much sexier than saving).
Super fit people avoid cravings by eating small, healthy meals throughout the day. The super thrift also do this - they buy here and there the things that are on sale before they have an urgent need to purchase them.
If you starved yourself for an entire week, you'd eat almost anything. Why do we think differently when we set our purchases to a schedule?