Every one requires a mentor. A mentor is the one who has gone through the path you are trying to follow. Mentor can guide you, challenge you to achieve thing which sometimes you believe is not possible by you.
To achieve great things in life you will require to have mentor. Mentor can be your boss, your friend, coach any one who can motivate you and give you right direction to follow. But some times its not possible or the mentor you have might not be able to give you enough time. In that case its best to start mentoring your self.
The easiest way to mentor your self is start self evaluating. Start pushing your self. Write down your Bigger goal and break it down in to task to achieve every day to pursue your final goal. Another way is start putting your self in your mentors shoes and try and think about questions your mentor will ask you. Try to ghost your mentor. This can give you insight which you might not be able to consciously acknowledge.
Hope this helps you too. Let me know if you have any other way to mentor your self.