Are the actions of the heart obligatory, or optional?

Hafiz Ibn Qayyim rahimahullah wrote Madarij al-Salikin, the Ranks of the Divine Seekers, which deals with the topic of Tasawwuf, and he writes: "The servitude of the man is divided over the heart, the tongue and the remaining limbs of the body. The issues dealing with the heart are sincerity, trust, love, patience, penitence, fear, hope, firm belief and true intention. The consensus is that these actions of the heart are incumbent."

He also writes: "If the heart is not cleansed then it will become foul, which will affect the entire body. The rectification of the heart comes before the rectification of the limbs. If the purification of the heart is ignored, it will be diseased." [Ibn Qayyim, Madarij al-Salikin, as quoted in Kandhalwi, The Inseparability of Sharia and Tariqa]