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
*** May these efforts be helpful.
Djang chub sem chog rinpoche, ma kye pa nam kye gyur chig. Kye pa nyam pa me pa yang, gong nä gong du phel war sho._()_**