Happiness is a perfume you cannot pour on others without getting a few drops on yourself.

Giving something away in this case does not deplete the supply. Cheering somebody up, making a room easier, doing a small kindness: these often lift the state of the person doing them as well, which is a fortunate arrangement and also slightly awkward, since it means generosity is never entirely selfless. That is no reason to do less of it.

On a flat day, the instinct is to wait until you feel better before dealing with anyone. Try the reverse. Do one small thing for somebody while still feeling bad, and notice the effect on your own afternoon. It will not always work, and it is no failing if it does not, but it is one of the few levers available from the inside.