My mentor at my current internship helped me improve my debugging skills. He's a great dev and has really good debugging skills. He showed me his ways of approaching things and how I should go about solving difficult problems.

I think he never directly helped me when I got stuck. I ask him like 'I have this confusing problem, can you help me out?' and he's like 'well yes, but actually no" and he almost always tells me that I can figure it out myself. And I do figure it out, eventually.

Now, I seldom feel the need to go to him. I guess that's a good improvement. :)