A man once came to the Messenger of Allah (saw), and complained that he feels hardness in his heart. The Messenger of Allah said, what translated means, "Would you like that your heart becomes soft and that you acquire what you need? Be merciful with the orphan, pat his head and feed him from what you eat. This will soften your heart, and enable you to get what you need." 

(Hadith At-Tabaraanee & As-Silsilah as-Saheehah)