Two small things happen side by side here: the speaker looks at the world, and the speaker cries. The tears "still shine" and the moon "still glows," and that word "still" quietly suggests something has changed in the speaker's life while the night itself carries on as before. The moon doesn't care, or doesn't notice, and keeps shining.
The last two lines are the turning point. Everything looks "brighter" because the speaker's eyes are full of tears. Tears blur and scatter light, so the moon seems to glow more intensely. There's a gentle sadness in that idea, since the beauty the speaker sees is tied directly to their pain. It isn't a dramatic or angry poem. The mood is quiet, tender, and a little lonely, like someone standing alone at night and noticing, almost against their will, that the sky looks lovely while they hurt. The poem never says why they're crying, and that silence leaves the feeling open for any reader to fill in.