Why do I feel bad 😔

why do I actually feel bad for having a bad day.. literally never have bad days.. my daughter is 4 days old, my sons 17 months and was just really getting on my nerves this evening. Asking my SO for help or even to play with our son is like pulling teeth.. so I’m making supper, playing toys, cleaning, bedtimes and also maintaining a 4 day old.. so I sort of snapped. I didn’t even get actually mad at anyone I just felt anger and rushed my sons bed time because he’s tired and needed to sleep. I feel so sad for my son.. I feel as if I’m hurting his feelings.. 😔😔