My decline cannot go any further now; the ultimate point is when you, O Saqi, come to believe in my repentance.

This couplet expresses a profound sense of despair and the speaker's reputation. It suggests that the speaker has hit rock bottom, reaching a point of such degradation that further decline is impossible. The second line ironically implies that only by falling this low would the Saki, or wine-server, actually believe the speaker's vow of repentance or abstinence. It highlights the speaker's past behaviour and the deep mistrust associated with it, where a change of heart is only credible when there's seemingly no other option left. It's a poignant reflection on personal lowest points and the struggle for redemption against a backdrop of past actions.