Because it is. Nursing M back to sleep and holding him with all the love of the world in my arms I realised that it's the not same with D anymore. It's not her fault, it's my huge, huge fear of what's "wrong" with her, what I've done to make it worse, not done, should be doing more of etc, etc. So every single one of my actions is subjected to this intense internal scrutiny - because basically it's ALL MY FAULT.
Good to realise this and move on. Now maybe we can have lazy days and just enjoy them.