There is a mathematical formula for growth. A study in Nature found...
Steve Magness@stevemagness
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Dec 27, 2025
~1 min read
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1
There is a mathematical formula for growth.
A study in Nature found that to maximize learning, you should aim to fail 15% of the time.
Too easy? You drift. Too hard? You quit.
It's the 85% Rule. The sweet spot for difficulty.
A study in Nature found that to maximize learning, you should aim to fail 15% of the time.
Too easy? You drift. Too hard? You quit.
It's the 85% Rule. The sweet spot for difficulty.
2
Psychologists call this the Zone of Proximal Development.
If the task is too easy, you coast and get bored.
If it is too hard, you panic, shut down, and say "why try?"
You need to be missing the mark occasionally to trigger adaptation.
If the task is too easy, you coast and get bored.
If it is too hard, you panic, shut down, and say "why try?"
You need to be missing the mark occasionally to trigger adaptation.
3
We often mistake this friction for failure. But it's the evidence that deep work is happening.
Frustration is a kind of green light, signalling this is important, we've almost found that pattern or new path.
Frustration is a kind of green light, signalling this is important, we've almost found that pattern or new path.
4
Think of it like lifting weights.
If the bar is too light, the muscle doesn't tear and rebuild.
If the bar is too heavy, you quit or give-up.
You need a weight that is a just manageable challenge.. The struggle is the stimulus.
If the bar is too light, the muscle doesn't tear and rebuild.
If the bar is too heavy, you quit or give-up.
You need a weight that is a just manageable challenge.. The struggle is the stimulus.
5
We tend to swing between extremes.
We either stay in our comfort zone where we feel safe.
Or we try to leap too far, go big or go home...and go home.
Neither leads to progress. You need to grasp the next rung on the ladder, not the top one.
We either stay in our comfort zone where we feel safe.
Or we try to leap too far, go big or go home...and go home.
Neither leads to progress. You need to grasp the next rung on the ladder, not the top one.
6
So ask yourself: Where am I coasting?
Where am I drowning?
And where is the edge—the place that feels hard but doable?
The margins are where growth lives.
Where am I drowning?
And where is the edge—the place that feels hard but doable?
The margins are where growth lives.
