Because of a health concern or other personal issue, you may have been absent from your employer for an extended period of time.  Explain to your interviewer that you kept in contact with your employer, but based on your personal or health issue, you felt it necessary to quit your job.  At the time you did, you did not know how much longer you would have been out of work.  In addition, you may have had an emergency that came up with your family where you had to leave but believed; based on conversations you had with your manager, that you would be fired upon your return.  If you are able to convince the unemployment personnel that you would have been fired upon your return, your employer would have to prove that they would not have fired you and what type of misconduct they would have treated the situation as.