A speaker who wants to be outside stargazing ends up spending the night indoors, and the poem is about making peace with that. Every night they see the moon and the sky, so counting stars is clearly a habit they enjoy. Tonight the rain has soaked their outside seat, and the plan has to wait until morning, when the sun is out.
The feeling is mild disappointment, but it never turns into complaint. The short, plain lines in the middle, "I can't go out so I stay in" and "I even made some coffee," read like someone shrugging and finding a way to enjoy the evening anyway. Coffee and music become small comforts that replace the stars. The last line, "I would think of things to relax me," is soft and a little unfinished, as if the speaker is still settling in. The mood is quiet, cozy and calm, with a hint of longing for the sky they can't see tonight.