Persistence?

Persistence, as defined by Webster, is to "go on resolutely in spite of difficulties." I am by nature a persistent person. Life is hard, and then it gets harder. But along the way there are wonderful gifts and joys that make it all worth while. Take for instance children. They are sweet and loving, and then they begin to grow up and they attempt to pull away from all of the love and instruction you are trying to give them. Raising children is hard, and it seems to get harder the older they become. However, despite all of the difficult times, you love them and they add great joy to your life - they are precious gifts. Professionals tell us everyday to be persistent in disciplining children. Why? They tell me that it will pay off in the end, and I believe them. Persistence is a good thing. I am persistent in raising my children to become productive, respectful, intelligent adults.
I am also persistent on my job. I am a high school teacher. If it wasn't enough dealing with the hormones of my own teenage daughter, I also deal with everyone else's teenagers. At work I can see my persistence pay off more quickly than in other areas of my life. I get the job done, result: people over me are happy, parents are happy, kids make better grades and actually learn something. I like my job.
Sometimes persistence is not so good however. Take my ex-husband for example. We have been apart/divorcered for four years now. I filed for divorce because he is an addict; he has abused many substances in the past but he is "getting older now" so he sticks to beer and presrciption drugs. The day I left him I begged that he go into treatment, if he would agree I would stay. He refused, so I left. I had been persistent in my attempt to make our marriage work for too many years and there had been no improvements, in fact, conditions had steadily declined. My ex however is an even more persistent person than I am. He has persued me since that fateful day despite my refusal to give him any more chances. He is determined to get me back despite having done nothing to battle his addictions.
I think Webster should add some conditions to his definition of persistence. For instance: persist only after what is just; persist after those things that will advance your life and the lives of others; know when to let go. If my ex would persist after sobriety, he might actually get somewhere with me (and his children). Persistence is a good thing, but it must be kept in right perspective and it must be positive.