“He has a right to criticize, who has a heart to help.” 
― Abraham Lincoln

“Criticism may not be agreeable, but it is necessary. It fulfills the same function as pain in the human body. It calls attention to an unhealthy state of things.” 
― Winston Churchill

“People ask you for criticism, but they only want praise.” 
― W. Somerset Maugham, Of Human Bondage

“The trouble with most of us is that we'd rather be ruined by praise than saved by criticism.” 
― Norman Vincent Peale

“Writers shouldn't fear criticism. Instead, they should fear silence. Criticism is healthy. It gets people thinking about your work and, even better, it gets them talking and arguing. But as for silence -- it is the greatest killer of writers. So if you hate a book and want to hurt it -- don't talk about it.” 
― Robert Fanney

“The motive behind criticism often determines its validity. Those who care criticize where necessary. Those who envy criticize the moment they think that they have found a weak spot.” 
― Criss Jami