Mentors are great because they love to impart wisdom, usually of their own volition. Most often, mentors share life advice and leadership skills that they've acquired through experience. No matter what problem you're facing, a mentor can be your best resource. Not only can they provide unbiased advice, they can also provide a wealth of emotional support.
Mentors may be an invaluable resource -- but, if you haven't found yours yet, there are some great resources online that can also help: great books to read, the newsletters to subscribe to, the motivational impetus, the calming forces, the must-use websites, services, or influences.
Happy exploring, and happy sharing.