Yoga Teacher Failure

What happens when a teacher fails in making a student be successful in yoga?

Does this teacher take another body, meet the said student and make the effort all over again?

These questions are considered by some students who suspect that there is no possibility of their succeeding with a process introduced by their yoga teacher. In fear of being left behind if the teacher transits to a higher dimensions, some students feel insecure considering that there will be no assistance rendered in future lives if that teacher is unavailable.

Does this mean that the teacher should be committed to taking birth after birth just to assist the said student?