It's about how love can be difficult sometimes, that not all things are rosy.
Yet, it is worthwhile to live it.
Don't you think that:
"Life means nothing at all...
If I don't fall...
In love with you..."
is the most beautiful thing to tell to someone you love?
Zazie's part can be translated as follows:
"Yes
I feel the wind
I feel the rain
Feel the pain
The blood running through my veins
Follows it's way
I follow mine
And it's so easy to live
And it's so easy to live
And it's more easy to live
Than to love you"
Yes the girl seems more pessimistic that the guy...