Rejection of forbidden thoughts causes great pleasure above:
Each time one suppresses and rejects a forbidden thought from being entertained in one’s mind he suppresses the side of evil. This causes that the source of evil above also becomes suppressed and shoots it down like an eagle who was flying high above and is now taken down from his haughty state. The Zohar [Teruma p. 128] elaborates on the tremendous pleasure Hashem receives when one suppresses the Sitra Achra in this world, and how it causes the splendor of Hashem to spread above throughout all levels, more so than any other praise can affect.
 Tanya chapter 27