strain at the leash
1. Lit. [for a dog] to pull very hard on its leash. It's hard to walk Fido, because he is always straining at the leash. I wish that this dog would not strain at the leash. It's very hard on me.
2. Fig. [for a person] to want to move ahead with things, aggressively and independently. She wants to fix things right away. She is straining at the leash to get started. Paul is straining at the leash to get on the job.