I have driven in many grounding rods over my lifetime, rarely has it been that hard to do, just be patient and watch out for your legs when swinging the sledge. One miss can be REALLY painful.
Alternately, you CAN use a Grounding Plate such as this below:
These can be installed 30 inches below surface and 24" from the building itself. These provide the same amount of "contact surface" as a 6' long rod but are more suitable in rocky soils and where a rod cannot be necessarily installed. I used these on my current home as I have rocky soils and it was far more practical & easier to do.
!*! Always check with your local Electrical Code requirements, they will ALL address proper grounding techniques for your region and such things should always be done to comply with codes.