This is a depressing picture, isn't it? For one of my friends who saw this the other day, it's simply hysterical that someone would hang this up as a poster on their wall. There seems to be no meaning to it because we all know that nobody would ever actually say "your best isn't good enough" to you unless they hated you. Well, that's true of most people, but not necessarily of Jesus and His disciples. Failure in God's eyes can be encouraging when it means more of Him who never fails. God, and those born of Him, are the only ones who can lovingly tell us that we will never be good enough on our own.
"Every man, I don't care who he is--even the strongest--every man that hasn't Christ in him, is a failure." ~D.L. Moody
So it's obvious that we will never be good enough because of our works, even if we are working zealously for God--check out Romans 3:23 if you need to be reminded. When we stop living by works, it means that we are shifting our focus from ourselves to God, which is also the way that we worship Him. The idea is not supposed to be a discouraging one; it's supposed to be a refocusing on who is more important. We fail in order to worship better. Failure, in that sense, produces hope, and it means that no matter what, even if you are feeling like the worst of scum, God is always good enough when you can't be.
“Beware of any work for God that causes or allows you to avoid
concentrating on Him. A great number of Christian workers worship their
work. The only concern of Christian workers should be their
concentration on God. This will mean that all the other boundaries of
life, whether they are mental, moral, or spiritual limits, are
completely free with the freedom God gives His child; that is, a
worshiping child, not a wayward one. A worker who lacks this serious
controlling emphasis of concentration on God is apt to become overly
burdened by his work. He is a slave to his own limits, having no freedom
of his body, mind, or spirit. Consequently, he becomes burned out and
defeated. There is no freedom and no delight in life at all. His nerves,
mind, and heart are so overwhelmed that God’s blessing cannot rest on
him.” ~Oswald Chambers