Mostly it's the sleep loss.
What I'm grateful for far exceeds all the negatives. Little things like watching her eyes steadily change from blue to hazel like a father. Her sister's eyes did the same.
Today the touch of golden brown that first appeared a week ago is brighter while the blue fades to a grey tint except for the dark ring at the edge that still looks nearly navy.
Part of the joy is simply in remembering.
There are other joys too. Seeing skills development. The day she learned to roll over. To sit up unassisted. I'm a huge fan of a kid sitting up by themselves. :-)
Her talking. As much talking as sounds that she thinks are words. Experiencing the act of communication. Hearing her big sister sing lullabies.
My favorite is her smile. Opened mouth. Displaying still toothless gums that even in silence say, "I'm so very excited to see you."
That combined with her obvious desire to jump into a hug delights me even when the day has been far too long.
Children are the best; even as they work you over to a crazy degree.