Once you can reliably bring up feelings of love in your heart, the minimum viable love practice should shift from “one loving thought per day” to “one loving feeling per day.” Of course, you are more than welcome to still think loving thoughts, to cultivate love in that way.
Once you are regularly cultivating loving feelings, you can begin to explore the territory of the spectrum of Love, learning to distinguish, feel, and cultivate different flavors of love, including the Brahmavihārās, gratitude, forgiveness, and bliss states.
Love is a spectrum, and the heart is boundless. Any and all positive, wholesome thoughts, feelings, mind-states, qualities, skills can be cultivated to great effect and benefit. As you can discern more and more positive feelings, use the same basic strategy to cultivate them.