It's better to work with a nice category containing some nasty objects, than a nasty category containing only nice objects.
Any effect, constant, theorem or equation named after Professor X was first discovered by Professor Y , for some value of Y not equal to X.
... commutative algebra is a lot like topology, only backwards.
Why speculate when you can calculate?
When somebody says to me-which they do like every 5 years- "How does it feel to be over the hill?" my response is, "I'm just heading up the mountain."