Proverbs 4:23 states it like this: “Above all else, guard your heart, for it is the well-spring of life.” The word picture here is graphic. The heart is a well from which all the issues of life gush forth. A youth pastor of mine growing up would say it this way: What’s in the well comes up in the bucket.
The behavior a person exhibits is an expression of the overflow of the heart. Why bring this up?
Evangelism and discipleship.
If when we are rebuffed while trying to share the love of Christ in the form of the sharing of the Gospel with others and they reject the message, our response tells us a great deal about our motives. If they reject the message and we respond with anger and hateful rebuttals, the conversation was about "winning souls" not the transformation of a life and transference of a soul from darkness to light. We've made the emphasis about ourselves and taken the rejection of Christ as the rejection of us. If, on the other hand, the rejection does not end the friendship or conversation, we truly are having Gospel conversations. You and I were most likely not saved on the first hearing of the Gospel. Have patience with new hearers. Show them the same love you coveted when you started out.
The same is true with discipleship. How you treat someone who struggles, stumbles, and falls in sin while trying to run the race of faith says more to do with your heart than theirs. A heart that loves, celebrates achievements in sanctification and encourages in the midst of failings.