Here's a wonderful quote by Horatius Bonar (1808 - 1889):
Not what my hands have done can save my guilty soul; Not what my toiling flesh has borne can make my spirit whole. Not what I feel or do can give me peace with God; Not all my prayers and sighs and tears can bear my awful load.
Thy grace alone O God to me can pardon speak; Thy power alone O Son of God can this sore bondage break. No other work, save thine, no other blood will do; No strength, save that which is divine, can bear me safely through.