Excerpts from 1966 press conference, in  Baseball: 8th Inning – A Whole New Ballgame https://www.youtube.com/watch?v=1ouIk6RvUl8 (1994) by Ken Burns, Geoffrey C. Ward 
Context: I don’t know if cortisone is good for you or not. But to take a shot every other ball game is more than I wanted to do and to walk around with a constant upset stomach because of the pills and to be high half the time during a ball game because you’re taking painkillers … I don’t want to have to do that [... ] I don't regret one minute of the last 12 years but I think I would regret the one year that was too many.
                                    
“I don't regret one minute of the twelve years I've spent in baseball, but I could regret one season too many.”
            1966 press conference announcing retirement, as quoted by UPI, in  "Sandy Koufax Announces Retirement from Baseball at News Meeting" https://newspaperarchive.com/pittsfield-berkshire-eagle-nov-19-1966-p-30/ by Alex Kahn (UPI), in The Pittsfield Berkshire Eagle (November 19, 1966) 
Context: I don't regret one minute of the twelve years I've spent in baseball, but I could regret one season too many. [... ] I've got a lot of years to live after baseball and I would like to live them with complete use of my body.
        
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Sandy Koufax 13
American baseball player 1935Related quotes
                                
                                    “Interviewer: What is your greatest regret?
Gorey: That I don't have one”
                                
                                
                                
                                
                            
Source: Ascending Peculiarity: Edward Gorey on Edward Gorey
“I'd rather regret the things I've done than regret the things I haven't done.”
                                        
                                        Variant: I'd rather regret the things that I have done than the things that I have not. 
Variant: Id rather regret the things that I have done than the things that I have not done.
                                    
Source: Reflections: Life After the White House