When you have to chase... cause if someone likes you back you wouldn't have to chase after them constantly. When the person shows no interest in you what so ever.
Most Helpful Guy
When you reach the goal mate!! That's when.
Feelings change all the time. As long as you're not going about your chasing... by stalking her, or harassing her.
There's no harm/or foul with keeping a little light flirting going if she's allowing it. Or not showing signs of disgust. Now hopefully you're a good observationalist, not that you have to be to know when a girl is annoyed by you lol.
But good luck man!! I got a girl by being persistent. This is a rarity I would say. And I don't advise doing so for as long as I did lol. It was pure hell and heartbreak before the bliss of you know what I mean.