I'M Thinking Poem by springy nothing

I'm thinking
They say that that's a first, but I'm thinking.

I'm listening
They tell me I'm fit to burst, but I listen

I don't understand...but then I do

I realize that I truely love you

I love you with a passion like no other
I will gladly lay my life down for yours.

But then I think about how long this will last

'Cause as a 17 year old child its been told to me by just about everyone that you and I, my 17 year old love, will not last.

'This is just a phase'
'You won't like him forever'
'He'll dump you'

But is it?

Can someone please tell me...if I feel so strongly and he feels the same...then why can't I have him forever?