In the world of finding love online, we encounter rejection much more often than in real life. And this applies to both sides: sometimes you get rejected, sometimes you have to reject. The ability to navigate this stage in an eco-friendly way is an indicator of maturity and readiness for a healthy relationship.
If you realize that the person is not right for you, you shouldn't use the tactic of «ghosting» (suddenly disappearing without explanation). This leaves the person hanging. It is much more honest and humane to write a short but polite message: «It was nice chatting, but I feel like we are looking for different things. I wish you the best of luck!». This demonstrates your respect.
On the other hand, if you were rejected, don't take it as a personal insult or proof of your unattractiveness. Often the reason lies not in you, but in the other person's circumstances or simply in the absence of that «spark». Accept the situation with dignity and move on.