Elevating Your Center of Gravity – How to Widen Your Window of Tolerance and Re-Center Yourself

Vertical development is a form of development that is focused on improving our internal operating such that we make meaning of our world in more cognitively and emotionally sophisticated ways.
Six Ways to Strengthen Your Mindfulness Muscles

I also find it helpful to think of mindfulness as a muscle. One of the things that you may have realized during the initial exercises is just how quickly our minds want to race off to other places. If our minds are really quick to race off, it suggest that our mindfulness muscles are weak.