In distance training, they’re called bricks.
The back to back long runs.
The second one is often… unpleasant.
Comfort zones are called comfort zones… for a reason.
Because they’re pretty damn comfy… even when they’re not.
But all progress is made in the discomfort.
When you’re hit with a brick, keep going.
Pile on the bricks.
You’re not born with resiliency and grit.
You become.