I think a lot of it is "whether you think you can or think you can't, you are probably right".
Also, successful people do what others don't, which is mainly activity or prospecting followed by product knowledge as it is always something you are learning as it changes.
Allowing personal problems or activities to interfere with what you should be treating like a business.
Lack of good training or someone or a team to take you under their wing. Not all need it but I'm one of those guys who likes and appreciates it and I feel it is rewarding on both ends. I feel that helping others to get what they want will help you to get what you want works in a lot of mysterious ways.
Lastly besides attitude and other items I listed would be work ethic. Your results are highly relative to the amount of time you 'buy' out of your life to transfer into your career. I'm speaking of quality time not oh I did this or that with no results. Refer to above points to see what quality time involves.
The lack of goals with a reasonable time frame. I'm guilty of this big time.
Good time management skills which BTW there is a few good threads on here about the subject.
Not being happy with what you do. If you aren't happy, you won't look forward to learning and honing your skills let alone with doing all the other thing I mentioned.
My .02 cents
I love your two Cents worth. I agree with you wholeheartedly. Especially the part about being happy with what you do.