Be as it may, I would be very careful in asking anyone to cancel your commitment. Adjuncts live in a twilight world where obligations are non-reciprocal (in other words, the employer can cancel the sections at the last minute.) Chairpeople have plenty of people to choose from, and they therefore have no hesitation in refusing to hire you again. It's a cost vs. benefit analysis, in other words.
So it is that the adjunct who follows the predominant advice of the fora, which is to use adjunct employment only as extra employment, is less desirable to the employer. The people who would defend the widespread use of cheap labor, if only they were truthful, want the person who relies on the income.