There's the obvious emotional connection, etc. but a new idea occurred to me.
Leah knows my body so well.
When I'm holding another child it can take them a minute to get comfy. To figure out how to snuggle into me.
Leah doesn't need this time or even a split second. When I pick her up her body instantly molds into mine. When she is sleeping - she will reach out in her sleep and wrap her arm around my neck or snuggle with her back to me & her head on my arm. She never opens her eyes or anything. She just knows where she fits against me instinctively.
I love that.
I love my daughter. I love her connectedness to me. I love that her physical connection to me is a thing of "instinct" and requires no squirming to get comfy.