{{{JZ}}} Please do not beat yourself up for not managing your emotions exactly the way you think you should. I'm pretty sure you didn't demand that M comfort you.
I am not a parent, but I am a daughter, and I am perpetually grateful for my mother telling me that crying doesn't have to have a reason. A completely different situation, of course, but she could only do that because her emotional life was also sometimes messy and I knew that.