This chapter gives us one of what I consider one of the most fundamental staples of Christian living. Through His teachings Jesus is describing principle-based living. We've been fasting as a church lately in preparation for the revival God's going to send. But when we do things like that, or participate in our, or even pray over our lunch every day, Jesus instructs us to be careful about our motives. If we're just fasting so we can say we did, or praying loudly just so people can hear how good we are at it, we might as well not do it at all.
When we do these things, the sacrifice is unto the Lord, and in secret. God will reward us openly. Let's keep our motives in check today, and do the things we do as if God's the only one watching, and base our lives off of principle, not rules.