The greatest enemy of the life of faith in God is not sin, but good choices which are not quite good enough. The good is always the enemy of the best.
Oswald Chambers - My Utmost For His Highest: May 25 Devotional
I have seen this concept in many business books, but it is interesting to see in a devotional such as this. Good is the enemy of great, because good is acceptable but may not be the best we can do, the best we have to offer. Good is usually good enough to get by, but getting by is not way we should be about it when we are talking our faith. Great is what we should strive for.
We know we will fall short of God's standards. He is holy and just, we are not. He is without sin, we are not. He is divine, we are His created beings; made in His image but not of His essence. And so we fall short, but He loves us anyway.
If you ask someone whether they think they are going to heaven, you will often hear something along the lines of "Yes, I am a good person". And they either believe (or desperately want to believe) that. No one says "Yes, I am a great person". But they will read that business book, that self help journal and nod their heads when it says things like you need to be great, that good isn't good enough.
"Yes, I am a good person."
"But good isn't good enough to satisfy the standards of a perfect God."
Personally, this "good" person is glad he has placed faith and trust in; that he serves a great God.