Sad goodbye...

It's not Red that meant to be Pink.
It's Violet that's meant to be blue..

It's not Good when we says our "Bye's"
It's not "Bye" that keeping our self sad..

it's a fact that.
We don't might see each other again.

We should say "See you" then instead of "Bye"

No. I think not.
If you two were meant to bump each other in a future Then good.
Sayin "Bye" or "See you" has nothing tp do with it..

You should not say
SEEYOU..
if you knew you can't live much longer anymore.
say Bye directly...
even of it is hard.