Sufi writing distinguishes two states and two temperaments. Sukr, intoxication, is the condition in which the mystic is overwhelmed, says things he cannot afterwards account for, and is not responsible in the ordinary sense. Sahw, sobriety, is the condition after the storm, in which the person has come back and can function. Junayd is the founder of the party that holds the second to be the higher.
His argument is structural rather than temperamental. Annihilation, fana, is real and necessary, but it is not the end of the road. What follows it is baqa, subsistence: the self is returned, remade, and set back down inside its ordinary obligations, so that the mystic prays, trades, judges and keeps the law like anyone else, with the difference now internal and invisible. A man permanently intoxicated has not completed the journey; he has stopped in the middle of it.
Underneath sits his doctrine of the covenant. Junayd reads the Quranic scene in which God addresses the not yet created descendants of Adam, asking whether he is not their Lord, as describing a state in which the soul existed in God before it existed in itself. The mystical path is therefore a return to a condition that is prior, not the acquisition of something new, and union is a recovery of what was always the case. That framing let him describe the highest states without ever asserting that a man becomes God, which is exactly the accusation the tradition needed to be able to answer.