Your poem is great... as it always is. So here... yet again...is my reply.
"Goodbye
I know that you can't stay forever
It would be wonderful if you could
But even though you won't leave now
Someday, I know you would
The world is just a cruel place
When we'll all just disappear
And when the ones we care for die
It seems pointless to stay here
It hurts that you have to leave
But I know that you can't stay
Goodbye for now, my dear friend
We'll meet again someday
Though when the time comes that we do
We would have forgotten everything
But I'll still look for you on the other side
Though I'm not sure about such a thing
You should know that I would follow soon
Because time will pass by fast
But for now, I'll hold on, though it's hard
And one day, I'll breathe my last
The time has come, you'll say farewell
Goodbye, my darling friend
I know I'll dream of you tonight
And I'll think of you 'til my end"
It rhymes... but It's still serious.