Purification is not to be confused with despair. One does think and even feel like one may be damned while one is experiencing the Dark Night. But, that is normal. To finally realize that one deserves to be damned for one's sins is pure gift.
The first realization of one's unworthiness reveals that one finds one's self, indeed, in the Dark Night.
That realization should bring about humility and, eventually, thankfulness.
Such are the purifications of the Dark Night that one finally doubts one's worth and one's false feelings.
Purification cannot be comfortable.
Read the long post series on the Dark Night, if you have not done so. Many begin in June of last year.