I think one of the biggest hindrances to knowing and experiencing the love of God together in communion as God's people is our failure to deal with sin issues. In our evangelical circles so much of the time there is a strong belief in "eternal security" in the sense that once someone makes a commitment to Christ and is really converted, then they're safe (and more or less sound, might be added). Whatever other reasons there are, I think that we too often ignore sins and issues that need to be dealt with.
Love does cover over a multitude of sins, as Scripture tells us. But we're also told not to let any brother or sister become hardened by the deceitfulness of sin, but to help each other daily.
We're all inherently part of the problem. Therefore we must always be seeking to deal with sin issues in our own lives, before we can be helpful to others.
When we see another sinning, or perhaps sinning, we can pray for them, and John tells us that God will give them life. There is also a time to prayerfully come alongside them, ask them questions, listen to them- though I think we shouldn't be in a hurry to do this. There ought to be sustained prayer beforehand. Of course the nature of the issue comes into play here as well.
Scripture indicates that sweeping sin under the rug does not mean it will go away. It will only grow and defile others. As Bonhoeffer points out, sin in the fellowship even when unknown to all except to the one sinning, is damaging to the fellowship. This is one major reason why too often we seem to know so little of the love and life of God in Jesus among us.
But we must start with ourselves. Are we ignoring sin in our own lives? Are we excusing it and justifying ourselves in it? Or are we confessing it to God, and if necessary to another, one we've offended? Are we seeking by God's grace to forsake it and go on in the way of Jesus?
As we do that we can then pray for our brothers and sisters. And pray that together we will experience anew the love and life of God.