I was very low and depressed earlier today (April 10), which is much less common now than in much of my recent (and distant) past; but it still happens from time to time. But my late night/early morning teaching has lifted my spirits. I feel that I am of use.
Confucius used to worry about whether anyone could use him ("yong"). This Chinese word doesn't necessarily have the same objectifying connotations as it does in English. It really means "being of service", just like the old saying that the highest good for a person is not to be served, but also to serve.
For me, this notion is not to be understood literally; it does not mean being weak and subservient, but rather, it means knowing that everyone depends on everyone else, in one way or another.
I have mixed feelings about the religion of Islam (and about any religion), but "whoever has done an atom's weight of good shall see it, and whoever has done an atom's weight of harm shall see it" is a deeply profound quotation from the central text of that faith.
If you can attune yourself to the small things you can do every day to benefit others, you will not worry too much about the "great and grand" things.
Remember that with greatness comes awesome responsibility, and with grandness comes awesome danger and peril.
As a wise Catholic (no doubt one of Kierkegaard's hidden Knights of Faith once told me: "Do not ever seek perfection. Perfection is dangerous. Instead seek excellence."