Having bad mortgage could make you frustration when this is not intended for you to do it. It could be caused by external factors. For example, when you are a entrepreneur, when you propose your loan to the bank, your business was running well, so cash flow in and out of your bank account looked perfect. The bank will approve your credit proposal. As time goes, your business went bad. You could not pay monthly installment, while your properties has been sold. This condition will make the bank assume that you have bad credit loans.
The same condition could happens also to employee. The company where you work grows well at the beginning, but after few years, the company has trouble with product sale, so the profit was not enough to pay salary to all its employees, and unluckily you are one of the suspended. You will not receive regular salary, and finally you could not pay installment regularly on time. Bank will mark this person as a bad debitor. In the future, the person will not be able to get loan from bank, except he had clean his name.
Actually, bank has done survey to your profile before approving your credit proposal, but sometime doing detail survey takes time, and bank is afraid of losing clients. So, bank usually will simplify the survey. This condition often happen to private banks, when the candidate of buyer seems has good financial profile. I had the same experience about this, the bank did not investigate me so deeply. This condition can be used by bad person to get loan from the bank by creating manipulative financial condition.