I don't think age has anything much to do with rejection. No one likes when people leave or die or move away/change jobs, etc.

I think a lot of how well we move on has to do with how well we know and like ourselves and are comfortable with what we are doing with our lives. If we haven't figured out what we want to do "next" and don't have much going on in the meantime, hard to cut ties?

I would think of times when you've changed jobs or moved when you were a kid and were looking forward to where you were going. When you want to end a relationship, start planning for the "next" thing and then it might not be so bad when it ends? I do try to remind myself to "turn around" and face "forward" rather than looking at disappointment in the past.