The speaker describes living with so many social masks that counting them is impossible. In public, they slip into whatever role the moment requires, and they can actually feel their face change as they do it. That sensation frightens them a little, but the poem admits they hide even that fear, so the concealment goes all the way down.
Then the tone turns. The speaker says the disguise isn't perfect: their eyes give them away. If someone looks closely, especially when sunlight catches them, the real emotion shows through. The ending hits hard. "Every. Single. Damn. Time." is broken into separate words, and the pause after each one makes it sound like frustration, relief, or maybe both. The speaker may be tired of performing, yet also quietly hoping to be seen. The mood is vulnerable and confiding, as if the speaker is finally letting one person in on the secret.