Critic

It is much easier to be critical than to be correct.

Benjamin Disraeli (1804-1881) British politician and author.

If you believe in what you are doing, then let nothing hold you up in your work. Much of the best work of the world has been done against seeming impossibilities. The thing is to get the work done.

Dale Carnegie (1888-1955) American writer.

Before you criticize a man, walk a mile in his shoes. That way, when you do criticize him, you'll be a mile away and have his shoes.

Unknown Source
Those who can -- do. Those who can't -- criticize.

Unknown Source ~

Don't mind criticism. If it is untrue, disregard it; if unfair, keep from irritation; if it is ignorant, smile; if it is justified it is not criticism, learn from it.

Unknown Source