Mentoring is a form of education, a word that derives from the Latin "educare", meaning "to draw out". The role of any teacher or mentor is to discover what the student does not yet see in himself, both the positive and the negative, and to help him draw it out, analyze it, and then make use of these discoveries in navigating his context of problems and opportunities.
Because each individual is unique, and his context unique, and his calling unique, advice must be sparing, and carefully crafted for the particulars of the individual case, recognizing the individual's internal and external resources and limitations. Better yet is to offer no advice at all, but rather to help the student frame his options as realistically as possible.
Perhaps the highest purpose of the mentor is simply to help the student make the implicit explicit, to pull out every unexamined assumption, and when required, force the student to the crisis point of deciding between incompatible options, while resisting the temptation to make the decision for him. In other words, a mentor is tasked with helping his student to be radically dedicated to reality, both his own subjective reality, and the objective reality which makes interpersonal collaboration possible.
Out of this process, the student should emerge with an enhanced capacity to accept rather than escape from his responsibility for the totality of his life and problems, while becoming better-equipped to move forward to solve those problems.