It might be worth trying to cling on then? Perhaps the mortgage people might be happy with you making a reduced payment in one month (especially if you have previously overpaid at all) to allow you to shove the "end of month" balance into the black so you can be more comfortable with it - that would obviously lengthen the mortgage but perhaps by less than agreeing a lower monthly payment for the forseeable future (or perhaps not, depends how much by I suppose).