Okay, I am not going to lie. I am not a persistent person nor do I have a lot of stamina. I give up quite easily. Recently someone had told me that she believes that one can achieve whatever one sets up to do, as long as he/she wants it enough. Not to say that being persistent is not a good trait, but I certainly hope that only applies to certain situations.
For example, when a man (or a woman) are too persistent about an object of affection despite their lack of interest, that's a stalker in the works. Okay, that maybe an extreme example. Some goals simply cannot be achieved with hard work and determination, e.g. becoming the next James Cameron. It takes hard work, luck, AND talent, and no amount of hard work can compensate for a lack of talent.
Sometimes, one simply needs to know when to quit.