There is another way to serve G-d-through awakening your heart to have mercy on the G-dly soul. Think how it felt with G-d before it came into this world and how it feels when you sin. This awakens you to do good and not bad. Through this, you can get a feeling of love to G-d in your heart because when you have mercy on someone you start developing love towards him, and the soul is part of G-d.