Rashi: If you will make Hashem's heart rejoice via going in His ways, He will put His face to benefit you, to do all your desire.

R. Yonah: Shlomo teaches that one should not think that there is no benefit or loss via thoughts of the heart, only via words and action. He brings a proof - the primary pleasure and pain of the body depends on the heart - "Lev Same'ach Yeitiv Gehah" (17:22). See the punishment of a heart that rejoices in sin and Iveles! It puts the primary bodily pleasure in sin, and it is recognized on his face! Considered the reward of a heart that rejoices in Mitzvos and is pained over sin. Resha'im rejoice over sin and evil - "Iveles Simchah l'Chasar Lev" (below, 21). Tzadikim's Simchah is in Avodas Hashem - "Sas Anochi Al Imrasecha", (Tehilim 119:162). This matter is very dear, therefore it is next to (verse 14) "Lev Navon Yevakesh Da'as." His Simchah is in Chachmah. Simchah is the root of all pleasure; it is recognized also in the body. A Chacham, his Torah brightens his face (Nedarim 49b); "Chachmas Adam Ta'ir Panav" (Koheles 8:1).

Malbim: Simchah and sadness of the heart can be in many ways. Here it discusses Simchah due to worldly matters - "Ki Libi Same'ach mi'Kol Amali" (Koheles 2:10). He is not sad over his sins or lack of perfection of his Nefesh. His heart rejoices in his success. This gladdens (and is recognized) only on the face. He does not benefit his Ru'ach, which includes all internal powers of the Nefesh - Ru'ach of Chachmah, Binah, Da'as and Yir'as Hashem. Sometimes the heart rejoices and the Ru'ach is sad and lowly, for he engages only in desires and Simchah of this world.

Rashi: If you will sadden Him, He will show to you an angry spirit - "va'Yis'atzev El Libo; va'Yomer Hashem Emcheh Es ha'Adam