Microprogressions and staying at the edge of performance

From the Jerzy Gregorek interview my Tim Ferriss (podcast episode #228)

Microprogression.

The anecdote he tells about the Baja 1000 racer saying that he has to stay at the speed between losing traction (too fast) and full traction (too slow), then push it a bit until he loses traction. That’s where the growth in capability is.

Same in weightlifting or any athletic endeavor. If you push right up to the level of your capability, then go a micro element beyond that — this is where you grow your capability.

So today instead of 5 km I ran more. Plus some stairs.

How do I extend this to my intellectual and spiritual affairs?