What is a core routine? It is a routine that once established, creates its own momentum and gravity, creates spin-off routines and habits, and shatters personal boundaries that previously contained your growth, efficiency, and effectiveness.
A core routine could be regular exercise, learning how to grow your own food, studying a subject or developing a skill that will pave the way to your dream job/career/business, or starting to create something that has never existed (like this blog, I hope!).
Routines are powerful ways to maximize your effectiveness through consistency, and also your efficiency by limiting the amount of energy needed to initiate an activity. Beginning and establishing a new habit/routine takes a significant amount of focus, energy, and commitment, but once ingrained- momentum takes over, and each time you repeat the routine, time and energy use is minimized, and becomes optimally efficient in terms of results gained over time.