I think, i heard, it is not a bad break of a vow. Means you don't reach hell for it. You are free to leave, but try not to talk bad about your teachers and about the mahayana - that is the only dangerous thing, to be contemptuous in speech.
The calculation is very simple: if you do the practice you will find a binding (samaya) to the teaching and to the teacher. If you don't, you will stay away from it. Nothing else happens.
Metta, Karuna, Mudita, Upekha
*** om vajra krodha hayagrīva hulu hulu hūm phat**