It's the fine print that will get you

Apparently, the ever-cautious Esarhaddon assessed a conditional self-curse on the citizens of Sippar. Yet the character of this particular malediction is very ominous. It is an arrat la napšur ‘a curse that cannot be released” (N of parāšu). Because Esarhaddon felt it necessary to include this statement, then we may read between the lines and conclude that, unless otherwise qualified, most imprecations were able to be undone in one way or another.— Cursed Are You!, page 321

<idle musing>
We're always looking for the escape clause, aren't we? Esarhaddon closed that one, but I'll bet somebody found another one. Remember that the Assyrians would sometimes adjust the calendar to avoid an ominous day...of course we would never do that! That's why there's so few 13th floors in public buildings...
</idle musing>