Never stop testing, and your advertising will never stop improving.
David Ogilvy
Never stop investing. Never stop improving. Never stop doing something new.
Bob Parsons
Employ your time in improving yourself by other men's writings, so that you shall gain easily what others have labored hard for.
Socrates
I'm actually improving.
Jenn Suhr
The day I'm not improving will be the day I hang up the racket.
Venus Williams
I have this desire to keep improving, so I find fault.
Heston Blumenthal