Had renegading bliss withheld from me
so, too, would cruelly parching agony.
What you don't have or have lost is what you most want, this is very human. We appreciate goods of any kind when they are at risk or no longer with us.
However, the poem goes further, literally stating that it is not advisable to drink aged elixirs because they can cause addiction and it is that there are as many sources of addiction for the human as there are sources of pain. We will never be satisfied, there will always be something that takes away our sleep or consumes us.
Once we get a taste of bliss (in whatever form) and it is then withheld (by the Cosmos? The higher Self? by Necessity?) we sometimes wish that we had never experienced such ecstasy, in comparison to which, the lack of such a feeling is pure torment.
That's right. Drinking from a fountain of happiness and then closing it, generates a stormy sense of emptiness, a thirst that does not end, and even in a way, abstinence.