The word life in this passage is the word psyche.
1) breath a) the breath of life 1) the vital force which animates the body and shows itself in breathing a) of animals b) of men b) life c) that in which there is life 1) a living being, a living soul 2) the soul a) the seat of the feelings, desires, affections, aversions (our heart, soul etc.)
Also our life is our time. What we spend our life, our time on. Jesus Christ laid down His physical life for us, for our sins, so we do not have to lay down our physical lives for our sins. We are free from the law of sin and death to live our lives and use our time to do what animates us and gives us peace in our soul, mind, will and emotions.
We can lay down our lives for our friends by giving of our time. Our time is our life. When you work and earn money, you are laying down that time, that life for money to feed your family and supply their needs. When you take time to pray and worship God, you are laying down your life for God. When you volunteer and do for others, you are laying down your life to help others. A little time (a little of your life) is laid down for whoever you take time to contact, pray for, call, send a note, even a "poke" on facebook to someone lonely is a way of laying your life down for others.
Ask a lonely person what they would like most and they will tell you, time with someone who cares. Children need their parent's time, not games, toys and material things. They need your life.
On Valentines Day, lay your life down for the ones you love. Give them your time.