Sayonara. Good bye. Auf Wiedersehen.
Initially I chose not to say “sayonara,” which means “so long good bye.” Instead, I rephrased to “Auf Wiedersehen.” It’s tenderer because it explicitly premises the next chance. At least it contains your wish to have another one. Or your world stays to the extend where the possibility still exists (regardless of “the fact”.) Au revoir and 再見 as well. Goodbye and adiós connote religious values.
Sayonara comes from a completely different angle compared to those above. Literally, sayonara originally/formally writes “sayou nara,” which means “if it is as it is, then.” You don’t sentimentally wish for another chance, but accept as is and depart.
At the end, sayonara was the right word.