Who's the boss?

I'm a good mom. Really. For someone who was never very maternal, never babysit unless under serious pressure, and often questioned whether they wanted kids at all, I actually turned out okay. I'm usually patient, kind, creative, and educational. They don't eat too many sweets or watch too much TV, and tantrums are usually controlled with quiet conversations to identify true needs and feelings. Today, though... today I have failed. M had tantrum upon tantrum, and try as I did to stay level-headed and find a solution, I couldn't do it. I feel like I gave up on him, finally just putting him down for a nap even though he was still crying as I closed the door. And now I can't even get a fussy K to fall asleep on my chest, even though she'll sleep with anyone else. So what's a mom to do? I have no boss. I have no one to go to in desperate times who can do my job for me, a senior person who can lift me out of this mess of my own doing. I look around, honestly frightened, to find the house empty and me all on my own. Other moms must have these moments, I tell myself, hidden from my sight as mine are from them. Or maybe, I think with even greater fear, I'm just not the mom I thought I was. Is trying hard--really really gutwrenchingly hard with the most love you can possibly squeeze from your soul--enough? I know nobody's perfect, but I look at these amazing little people in my care, and I feel that they deserve perfect anyway. I'd hate for them to be as disappointed in me as I am in myself.