A good mentor or mentor can provide a clear map / blueprint of the order of things to learn and what to do in order to be successful. This is based on a lot of experience and learning possessed by mentors or mentors.
A good mentor or mentor can motivate you to take the first step that is usually the most difficult for you to do.
A good mentor or mentor can help you focus more on learning and doing the most important things first and help you ignore things you don't need to know (This is very important when you have access to unlimited information like today) . People with most information generally get confused and never take action!
A good mentor or mentor can give you enthusiasm / motivation to get back up if you are down or discouraged when facing difficulties or challenges.
A good mentor or mentor can give you help with ideas and solutions when you face a dead end because he already has a lot of experience and knowledge in the field.