Decide from the beginning that either party can bring grievances without fear of reprisal. Talk openly about any concerns that arise and agree to listen without judgment.
Discussing issues openly and honestly allows the either party space to alter their approach and proceed more effectively. Of course, a mentor-mentee pair might realize that the mentor is requiring more of the mentee than they are willing to give. This is a could strain the pair but working through it also provides an opportunity for the mentee's personal growth.
Neither the mentor, nor the mentee should ever feel that they can’t mention something that’s bothering them about the relationship. If this occurs, likely, the mentorship is already headed into unhealthy territory. If problems can’t be discussed, then the best thing to do might be to involve a third-party and try to work through difficulties.
Address issues quickly to salvage and nurture the relationship. Don’t ever let yourself be overwhelmed. On the whole, mentorships should be a positive experience. If yours isn’t, use the opportunity to learn about your personality traits and develop your communication skills to make the relationship work.