Michaella Bruezella points out in Sojourner's Commentary the challenge in this command:
Indeed, our hardest task is not loving one another, but doing so as Jesus did—recognizing each person’s ability to receive God’s grace, and then serve as its ambassador to the world.Remember, Jesus was preaching to people living in hard times, and John's gospel was written to people who knew loss and were facing more difficulties. To these people, at that time, came the command to love.
When we have suffered loss, when we fear disruption in our community, when we don't feel in control of what is happening or is going to happen, we still need to heed that command, "Love one another as I have loved you."
To be able to withstand difficulties and disruptions, we must love one another--and remember what love looks like.