I don't know that there is such a thing as a perfect session, especially when photographing your own child. I'm sure that plenty of other photographers out there will tell you the exact same thing.
It's like an unspoken curse or maybe just a higher expectation (& lower tolerance) from your own kids to behave the way you want them to & to make pretty faces, or follow instructions. Either way, photographing my own children is almost always 100 times harder & more exhausting than any other session, hands down.
If you see an image you like or even love, you can bet that there are at least 15 like this for every one of those:
Oh the unpredictability of childhood, it's pure bliss!