I don't see relationships that way. Once I get to know a person and spend some time with them, have mutual memories etc. I consider them as someone I could renew a contact with if I want to. Only if they explicitly tell me to not contact them and leave them alone or don't even respond I'd understand it as rejection. I'm weird like that.
Most of them don't leave. They are busy with their life and have other priorities than interacting with me.