Nos,
I really enjoyed your post. It has personal significance to me. Last month I graduated with an associate's degree in Paralegal studies. It took me three and a half years to complete as I did it part-time by night and summer classes. A few weeks ago, I said to my husband, "You know, I'm a bit surprised and proud of myself for having hung in all that time and finishing school." He looked at me and said, "I'm not. You're tenacious!" I asked, "Is 'tenacious' your code word for 'nag' or 'P.I.A'?" He said, "No. It's one of your good characteristics; when you say you're going to do something, you always do it and it forces me to get things done that I might not have without you."

I have been thinking about it since that conversation. Your friend is right in that it is not about being better than someone else, it is about being a better person. I do prefer the term "purposefully tenacious."