Wow! I looove this... First I love how you compared this person to a cold winter but also a warm fire... it shows that this person can be a nuisance to you, but also someone who keeps you warm and is essential to your life. I think this is a topic many people can relate to in different ways..

The first two stanzas were my favorite. They were so powerful and the imagery was amazing.

"You are my everlasting winter"
^ this part made me feel like this person is always 'cold'

"but..you're also
the fire, that burns deep down,
the warm sun that shines
from beyond the grey sky-
when least expected."
^ so beautiful! I loved everything about this stanza. It was so powerful and affected me.

"And I'm not sure
if I should be happy,
and I'm not sure
if I should be sad,"
^ this stanza was simple yet important to this story you tell. You're not sure if you should be happy because of the good times you have with this person, or if you should be sad because of the bad times you might have. And I feel this is a legitimate question to ask yourself... to find out if it is all worth it in the end.

The ending confused me a tiny bit. As I kind of was hoping for a more clear ending... maybe what you concluded after being unsure... or perhaps this is what you intended... to leave us as the readers guessing.

I really enjoyed this poem. Great job!