Because your blood group is O RhD negative, it is very special indeed.
It can be given to anyone. That means your blood is the only safe option when a patient's blood group is unknown or not immediately available - such as in emergencies, or in the case of specialised procedures for unborn babies.
So you can be absolutely certain that you are helping save people's lives.
You can give blood three times a year, so please be sure to keep up your outstanding work and donate every four months if you possibly can.