Mentors come in a lot of shapes and sizes in my life. I can't point to a single person or one single piece of insightful advice. When I look back, I see the long line of people who dropped tidbits of encouragement, advice, and tutoring. I look back across the vast sea of books I'd read that taught me how stories come together. I had RWA teaching me everything I needed to know about writing an about the business. I also had Jeffe trying to mentor me in networking - I was not her brightest pupil. Eventually, it was the people willing to critique my work and talk me through what was right, what was wrong, and how to fix it. I needed someone to take me by the hand and say this is wrong, do you see it? Here's how you fix it. I learned so much that way and I was so grateful for that education.
As for reaching back to help those coming up, I critique for others. Usually it's within my own critique groups, but the real fun is critiquing for contests. I want to help newer, younger writers learn what I learned from critique.
I needed direct 'this is wrong, see? Do this. Or this.' I have come to understand, however, that I'm in the minority and most people do not want me approaching their fiction in that fashion. So I've had to adapt. I've learned to say things like, what's the goal of the scene? What does this character want right here and why? I guess I've had to learn to lead people to see their own issues themselves rather than have me come right out and say hey this doesn't work here's why and here's how to fix it. It's a running joke with my critique groups that you'll always here me say 'I feel like you have an opportunity here to do xy or z' which is my way of saying hey you missed a potentially potent story thread. I hope it helps.
As for me, I still need a mentor. I need someone who can mentor me in cloning myself so that one of me can do the day job and care for the elderly parents and the other one of me can write and take care of cats and the rest of the household. I'm not sure that kind of mad science is in anyone else's best interests, though.