From All Is Happiness (#E-060) by Rabbi Avigdor Miller
Most people in the world don't understand why they were created. Well, to do mitzvos. You certainly have to do mitzvos. But you must know, the mitzvos that the Torah commands you are very few.
How many people will ever do the mitzvah of peter chamor (you have to redeem the firstborn of your donkey)? You don’t even have a bechor of a beheima tehorah (first born if a pure species); you're not a man who has livestock. When will you give away your bechor to the Kohanim from your livestock, from your sheep and your cow? How many times in your life will you encounter a kan tzipor, a nest of a bird, and fulfill the mitzvah of shiluach hakein (sending aware the mother bird)? Maybe never.
Most people don't understand why they were created
How many times in your life will you be able to do the eglah arufah? You can’t do it anymore. The korban chatas (sin offering)? You can’t do it anymore. So many things that come up rarely. Or the ben sorer umorer (wayward son); these things never happen.
There are very few mitzvos you can do. So how do you serve Hashem in this world? Put on tefillin? Put on a tallis, say Krias Shema, and Shemoneh Esrei; and that’s all, forget all about it? That’s not called serving Hashem. Serving Hashem is “bikar byom tova — if it’s a day of good — heyei bitov — be happy that day and sing to Hashem."
When it’s the springtime, say Hashem we thank you for the spring; the flowers are coming out, the trees are beautiful, the air is fresh. We sing to you, Hashem. In wintertime, the air is brisk, it’s healthy, it’s clean fresh cold air, right out of Hashem’s refrigerator. Breathe in the air and thank him for the fresh air. Summer, spring, autumn and winter — every season has opportunities that are byom tova. That’s our function in life.