If doing that mitzvah you just did, did not make you happy then you did not do it right. Mitzvahs are specifically designed to increase our awareness of Hashem's presence. That is their primary purpose. When one experiences Hashem's presence there is tremendous joy. Even if that mitzvah did not reveal Hashem's presence completely, still, if it increased your awareness of His presence as it should have then you should have experienced an increased measure of joy.
Hashem is everywhere at all times but He hides in order to give us a reward for finding Him. When you do a mitzvah the clouds that cover our spiritual awareness thin somewhat making it easier to see that He is truly here. Look for Hashem's presence when you do a mitzvah.