Only let you manner of life be worthy of the gospel of Christ, so that whether I come and see you or am absent, I may hear of you, that you are standing firm in one spirit, with one mind striving side by side for the faith of the gospel.
The life "worthy of the gospel" described in this verse is not in line with our natural tendencies. We tend to drift rather than stand firm. We tend to be selfish rather than sharing "one mind". We delay and procrastinate instead of striving for the gospel. We prefer to operate as isolated individuals rather than striving side by side with our christian community.
The good news is that we can stand firm because we know God is in control and we are not. We can be united because we recognise that we are all sinners dependant on God's grace. We can strive for the gospel because we see that Jesus laid down His life for us. And we can do this side by side with other believers as we extend love to others, motivated by the undeserving love God has shown to us.