Mesilat Yesharim
When you look further into the matter, you will see that true perfection lies only in clinging to G-d. This is what King David said "But as for me, closeness to G-d is my good" (Ps. 73:28) and, "one thing I asked from G-d; that I seek, that I may dwell in G-d's house all the days of my life, to gaze on the pleasantness of G-d..." (Ps. 27:4). For only this is the good, while anything besides this that people consider good is really emptiness and mistaken worthlessness.