You always paid your mortgage on time but suddenly you can't-perhaps you've fallen ill or lost your job. Tell your lender the situation. Try to renegotiate your mortgage to reduce the monthly payments - by extending the payment period, for example. (if you're regularly behind with your payments, however, your lender may not be so understanding.) Ask your lender how long you have to make your mortgage payments before repossession begins.
If your mortgage is called in, your home may be sold at auction and the proceeds used to pay off the amount outstanding on the mortgage plus any incurred costs. You may get nothing. It maybe better, therefore, if repossession is a real threat, to sell your home (if possible), pay off the lender, and put the remaining amount into an interest-bearing savings account.