My 8 month old puppy gets out of control how do i calm him?

My 8 month old mastiff puppy goes nuts at night some times when i take him out in the back to run. He acts like hes on crack and jumps up on me and nips pretty hard. The more i tell him to stop or push him off the more he tries to bite and pounce because he thinks its a game. I try to pin him on the ground if i can but it doesnt always work. What should i do?