People around you affect you in more ways than you may be aware of. Here is a piece on developing mental toughness, that categorizes people into doubters, leeches, critics, envious, victims, the noise. Read the article..
This, is no doubt, an interesting way of putting people into boxes. There is also no doubt that some will surely identify real people around them as of those types.
But does it help you? I doubt. Mental toughness and other qualities of mind needed for leadership can be developed by introspection, analysis of situations, synthesis of action plan, and implementation.
People around you can help or throw obstacles only if you are set on a course. You can draw inspiration, learn from their mistakes, or avoid them if it becomes necessary but need to be on your own course, very much.
I have another problem with the article. It is unfair and unnecessary to type cast people in this manner.
To develop leadership skills (mental toughness is part of leadership qualities) consider these programs
Learning Leadership at http://www.learning-leadership.com and the Lead to Regenerate workbook http://www.learning-leadership.com/blog/lead-to-regenerate/
The above programs help you in introspection, analysis of situations, synthesis of action plan with help of workouts.