From All Is Happiness (#E-60) by Rabbi Avigdor Miller
The happiness of learning Torah is one of the forms of enjoying Olam Hazeh (This World). You have to understand that: Torah is a great happiness. When they came to Har Sinai, and Hakadosh Baruch Hu began to speak, it was “Nafshi yatzah bidabor — My soul went out of me when he spoke” (Shir Hashirim). We perished; we had to be revived. It was a tremendous sweetness to hear the words of Hashem. Hashem’s Torah is the sweetness of life.
Any perfection that we achieve is a form of happiness
From then on, whenever you open a Chumash, try to gain a feeling “hanechemadim mizahav umipaz vdash vnofesh tzufim”: The Torah is sweeter than honey (Tehilim 19). Now Dovid Hamelech trained himself to have a geshmak (thrill) in Torah, to feel the pleasantness of Torah. Of course now we are far away from that concept, but we know that our neshamos (souls) are really happy with Torah. When people regale themselves with a feast of Torah, they should know that they’re enjoying Olam Hazeh, too.
Therefore we look back to Matan Torah (the giving of the Torah) and we say “Mi yishakeini minishikos pihu — Once more, you should kiss us with the kisses of his mouth — ki tovim dodecha miyain — because Your love [when You told us words of Torah] is better than any wine” of happiness of This World. Now not only Torah, however. Any form of shleimus, of perfection that we achieve in this world is a form of happiness.