Take time to have fellowship with other pilgrims of faith. That is the school of love. There, with other unlovables, you will be able to exercise the muscle of love that the Spirit will grow within you - live out the command of love. Have a look at Hebrews 10.24-25 for background there. Practice the act of agape loving.
Spiritual muscles are like body muscles.
If you don't use them, they weaken. One of the great truths of the Faith is that God supplies what we need when we need it. Like manna in the wilderness, God nourishes us, grows us, develops us as we need it. To grow in His love we need to give away the love He already placed within us. To share it.