"It is not the critic who counts, not the man who points out how the strong man stumbled, or where the doer of deeds could have done better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood, who strives valiantly, who errs and comes short again and again, who knows the great enthusiasms, the great devotions, and spends himself in a worthy cause, who at best knows achievement and who at the worst if he fails at least fails while daring greatly so that his place shall never be with those cold and timid souls who know neither victory nor defeat."
~ Theodore Roosevelt From a speech given in Paris at the Sorbonne in 1910
Failure is inevitable, the critic will always be there, but ultimately it is you who decides to either succumb to the opposition or continue on in the face of it all. Only one of these has a guaranteed result. If you quit you will never see success. Guaranteed.
"Never give up, never surrender!" - Galaxy Quest. It may come from a comedy but I find it a handy phrase! :)