Relate.

To those outside the church the relevance of our Gospel hangs on how we relate to one another.

We are comfortable with history confirming Jesus' existence as well as what he did. We are comfortable with the Bible verifying who Jesus was and the success of his mission. Indeed if we were in a debate on these issues we'd win, no worries.

We are comfortable with all of these things because it means that validity of the Gospel is independent of us, but that is not the case. To the watching world our lives [if they deny Christ in our actions, reactions, words, attitudes etc] can completely undermine the power of the Gospel.
Yes, the Gospel of Jesus Christ does have the power to save but the world will never look at the Gospel unless they see it in us first, and the way they see it is in how we relate to one another.

Let's be honest if you went into a church full of people who didn't join in with the worship [or indeed anything], where they stopped listening to the sermon and even walked out before it had finished. Where you heard people complaining about the worship band immediately after the meeting [as though it was a performance requiring some academic appraisal], you would surely wonder if that church had anything to offer you.
Wouldn't you?
This is because they are not characteristics that would inspire you to join a group, driving you on to understand what gives them their vibrancy. The church [our church, each of us] should have qualities that anyone should find unbearably irresistible:
"Therefore, as God's chosen people, holy and dearly loved, clothe yourselves with compassion, kindness, humility, gentleness and patience. Bear with each other and forgive whatever grievances you may have against one another. Forgive as the Lord forgave you. And over all these virtues put on love, which binds them all together in perfect unity." Col 3:12-14

They say 'when in Rome do as the Romans do', equally 'when in church [which is God's family as well as yours] do as Jesus did'.

If we captured this quality in our relationships with each other we would be simply irresistible, we could forget about outreach programs because we would be too busy discipling the people being added to God's family [hungry for real godly family relationships] on a daily basis.