Feeling of 'despair' during milk let-down

I'm not sure if despair is the right word for what I feel when baby starts to feed, as it is a feeling I've never had before, but, man...it is intense. It feels like sadness, happiness, euphoria and tiredness all at once. I hope it's just a hormonal response...but does it last throughout the whole bf journey? Does it ever go away? Do you guys feel something similar? How would you describe it?