1 John 2 -
15Do not love the world or anything in the world. If anyone loves the world, the love of the Father is not in him. 16For everything in the world—the cravings of sinful man, the lust of his eyes and the boasting of what he has and does—comes not from the Father but from the world.

I'm convinced from my own life that if I walk in a lack of love it comes from pride or lust. How does a person walk in love? Is just praying for God to make me loving going to fix it? Is just trying harder going to work. As humans I'm convinced our own strength to love others (we are talking 1 Cor. 13 love) is extremely minimal. Virtually non-existant. But Jesus constantly focused on love even up to his death (John 15:12). I'm convinced that like anything else in this life the concept of bad root/bad fruit applies. So what's the bad root in a person's life that causes God's love to not flow through them. I'm convinced 1 John 2 is the answer. In order to let God's love flow through me, I need to not love the world. So what is defined as the world. The cravings of sinful man, lust, and pride. If those things are out of the way, love will flow from God to me to whoever I come in contact with. If they aren't, than I will basically have nothing to give (1 Cor. 13).