bit between one's teeth

If he was to get the bit between his teeth after he had got ordained and bought his living, he would play more pranks than ever he, Theobald, had done.

The upheaval in the creative unions seems to have gone further than expected and the forces for renewal took the bit between their teeth — to such an extent that the writers' congress in June of the same year would follow more staid formulas and attempt more of a compromise between the old and the new, as compared to the Fifth Congress of the Filmmakers' Union in May, where the old guard of film directors had been eliminated (Lev Kulidshanov, Vladimir Naumov, and Sergei Bondarchuk).

Some fellow British travellers at Xian, who own horses and therefore understand equine tack, pointed out — when I asked about the authenticity of the replicas — that the horses could not possibly have coped with the bit between their teeth (as they were shown) for long.