No is a difficult thing to say and hear, but it’s one of the best answers you can give someone. It lets them know that a door they’ve been knocking on is closed. It signals an opportunity to move on.
It’s OK to move on.
If the door is closed the issue isn’t that it’s closed, it’s that the effort has to shift to something different, maybe unfamiliar or uncomfortable.
Despite your reluctance my guess is that you’ve dealt this different, unfamiliar, or uncomfortable before. You can do it again. Odds are at the end of it your reality will likely be far better than what you’d originally envisioned.