You've had several mentors throughout your life. They've all been different, yet the same. You've also been a mentor yourself.
As a mentee, you follow, assist, and in some ways, admire your mentor. You predict and learn your mentor in order to be of best help. Along the way you learn many invaluable lessons.
“Mentorship is simply learning from the mistakes and mastery of a successful person in his/her field.” - Bernard Kelvin Clive
As a mentee, you get to filter out the bad and soak in all the good.
“Just about ANY personality trait or skill can be learned: simply find it in someone you know and copy it. Then watch what happens.” - Steve Goodier
As a mentor, on the other hand, you get to see a younger reflection of yourself. Someone who's learning and walking the path you've walked a million times before.
You become courageous once again in order to create a positive influence on someone else.
As you teach, you rediscover all that you've learned along the way.