Most Christians understood that they are justified not by their works, but through their faith.
Some Christians understood that their faith to be based on God's grace alone.
Fewer still put this understanding into practice.
Example of distinction:
When one is given a credit one does not deserve,
one disappears before it is given one, avoiding the chance to refuse all together.
[This is the natural reaction of a work-based principle]
one accepts the credit, and then gives it to those who actually deserve such credit.
[This is the working of a grace-based principle]
Resource: When I was told about a case (David Tong), whether it be true or not I cannot verify, where he was given the honor to speak by his father on the stage, he disappeared, because he thought that there were others who were more deserving to receive such honor. I thought there was something wrong then (a few years back) but I couldn't pin point it, now I know what it is.
It is easy for us to claim that we base our foundation on Sola Gratia. Yet we need to constantly work it out into our lives beyond textbook memorization of orthodoxy.