John 15:12-17
These things I command you, so that you will love one another. (John 15:17 ESV)
When I think of love I think of something that is voluntary. It is something that you decide, not something that is forced on you. And that is exactly how God created mankind.
We were created with the capacity to love, but not forced to do so. No one makes us love anyone. But we do love don't we? We choose over and over again to risk our hearts in loving other fallen creatures like ourselves.
Jesus epitomizes love. He even at one point stated it matter-of-factly, the highest form of love is self-sacrifice. And he called his followers to join him in that. Self-sacrifice doesn't always mean voluntarily allowing your mortal existence to end so that someone's life can be better. In fact, some of the highest form of selflessness comes when you soldier in through something immensely difficult in order to help someone. That is love.
Those who profess to follow Jesus in their faith, beliefs, and practices are asked to be willing to serve one another selflessly. Jesus wants us to go the extra mile for each other. He wants to love one another deeply, and authentically. Love is voluntary, and yet the Christ of Christianity commands love.