I am astonished that you are so quickly deserting him who called you in the grace of Christ and are turning to a different gospel-not that there is another one, but there are some who trouble you and want to distort the gospel of Christ. (Galatians 1:6-7 ESV)
The gospel is the heartbeat of Christianity. The truth that God has come in grace to forgive our sins is the key that unlocks an understanding of truth and life. The ripples of that message should be felt in every area of your life. This should be a truth that we understand, feel deeply, and are ready to defend and die for. It should be apparent that this is exactly where attacks to the truth will take place.
However, what may not be apparent is where those attacks will originate. We would expect them from those outside as they seek to discredit this truth, but what about from the inside? What about the religious? Wouldn't they be die-hard defenders? Galatians is a hard book that calls us to awareness and defense of the gospel. It's Paul's strong cry to be aware that the gospel will be attacked, but maybe not in the way you think.