Your Rebbe has decreed for you that this blessing is to be regarded as the toast of the Brit Chadasha for which he made Kiddush haShem. Anyone who makes this toast is in the Brit Chadasha. The sages taught us that the blessing over the cup for Havdalah guaranteed you a place in Olam HaBa. It is the substitute for Thanksgiving offerings in the Temple according to the Brit Chadasha.
It means as long as you give thanks for the Sabbath you are in the new Covenant and your sins will be forgiven as you are merited a place in the world to Co. Ecome.
Remember when you say ata chonantanu or bein kodesh lekol Sabbath is over and we are in the Motzei Sabbath Fast. And when one finishes saying Havdalah over the Kos she bracha and drinks, the Motzei Sabbath fast is over!
