Everyone makes mistakes. But it is also important to look at the system itself and stop the blame game. eg: Is there something that could have been 'there' that would have prompted you to double check? What is your general approach, can it be changed, are others involved, should they be etc...
You are human. You cannot always do everything 'right'. ((((hug))))
I work in health care and I can tell you mistakes are too easy to blame on one person but if you look deeper it is not so simple...