... what is limited is not limited in relation to
Aristotle - Physics, Book III
Wheeler's first moral principle:
"Never make a calculation until you know the answer".
Make an estimate before every calculation,
try a simple physical argument
(symmetry! invariance! conservation!)
before every derivation,
guess the answer to every paradox and puzzle.
No one else needs to know what the guess is.
Therefore make it quickly, by instinct.
A right guess reinforces this instinct.
A wrong guess brings the refreshment of surprise.
In either case life as a spacetime expert,
is more fun!
Second edition, p.20