I think that quote is a good one to illustrate this verse:
The heart is deceitful above all things
and beyond cure.
Who can understand it?
Jeremiah 17:9
The problem is that most people are more focused on guessing what is in someone else's hearts instead of working on what is going on in their own. If you want real Christian growth and the blessings of intimacy with God that come with it, focus on weeding your heart, and let the Lord take care of them. I try to imagine myself standing before the Lord and explaining myself. That exercise helps me in two ways. It makes me realize how very significant my sin is and how very insignificant others are in how I live. Excuses won't fly with the Lord. Get real in your walk!