The speaker has just run into someone they once loved, and the shock is right there in the blunt "Holy shit." Old feelings try to creep back in, but this time the speaker refuses to let them. The words "Not this time" suggest it has happened before, and that giving in has hurt in the past.
Still, resisting isn't easy. The repeated "Damn how much I wanna..." shows the longing breaking through the effort to stay in control. The speaker admits they want to love and hold this person, then shuts the door on it: it "won't" happen and "never will." The mood is raw and conflicted, a mix of desire, frustration and tired acceptance. The casual, unpolished language makes it feel like a thought blurted out in the moment, not a carefully shaped speech. We don't learn why the relationship can't work, and that gap leaves the ache unexplained but real.