I agree that persistence and perseverance are good abilities to develop. I would also suggest that sometimes continuing forward to the next "Yes" can be more productive and healthier than spending twice as much time dragging an unenthusiastic "yes" from the first contact.

Perseverance sometimes means being told "No" and being able to make the next contact with the same enthusiasm you had before the last contact.

We have all been pestered and annoyed by salespeople who just won't take no for an answer. I wouldn't want my sons or daughters to become like them, but like you, I do want them to learn persistence and perseverance regarding the project or goal as a whole.

Over the years I have had more fun and have received more referrals and repeat business from those clients who enthusiastically wanted to work with me than with those I had to convince to work with me.

Today, I work exclusively with the enthusiastic clients. Most of them are referrals from past clients who I didn't have to use any persistence or perseverance with. Could I have persevered and persisted more with some potential clients? Could I have possibly convinced them to work with me? Sure. But quality of life and enjoyment of one's profession often has a lot to do with who you associate with regularly (i.e. who your clients are). I highly value enjoying my job and enjoying my clients.

Sometimes it is better (for both of you) to let some people go.