Why Can't I Be Supermom?

Lately I've been feeling a little down. Nothing major, but just slightly off. It's funny because after baby I was so worried the "baby blues" (ugh do I hate that stupid term) would hit me. And it didn't. With the first baby, it certainly did...and it lingered for quite awhile. But this time was so different...squeal?
I did try to mentally prepare myself the second time around, and I knew what to expect. No, the house wouldn't be cleaned for months...in fact, it wouldn't ever look the same again. I would be home alone with a baby all the time, and that might get tiring...annoying...lonely. It's ok...I could deal. (And I have little C this time, so things definitely have been less lonely.)
So far I've nursed baby L at least three months longer than little C, so for the most part my hormones have been even as can be. Until they haven't been. What. Has. Happened. This. Week.
Baby L is a great baby. She nurses well, doesn't fuss too much, eats her veggies, and even wears those huge silly bows I adorn her with without much of a fuss. She sleeps in her crib pretty darn well, waking once at night right now. (Which is way better than the every three hours she did for ages.) She hasn't had a single ear infection (knock on wood) and barely a cold.
Lately though she hasn't been napping very well. She will sleep on a stroller ride. Problem? She falls asleep on the last lap, ending my walk at 1 hour and 20 minutes. Le sigh. Slightly tiring when you've had all of six hours of sleep, but alas...pretty sure I've lost the baby weight. She's a major car napper. Problem? I find myself taking the easy way with this option and spending entirely too much on gas, wondering if certain neighborhoods I drive through have a stalker warrant out for my arrest yet. And...I don't get a nap myself. So, there's that. I will nap with her when I can, but...she's been incredibly hard to go to sleep lately. And even when I rock her in my arms and try to put her down for a crib nap. She's not having it. And here sets the stage for my feelings of incompetence.
Why can't I be supermom?!
You've read countless articles and posts about how it's ok to let things go...we can't be supermom. Or...how mom X learned to just be herself and embrace her carefree life and falalalala. She's such a better person now! Or mom Z stopped yelling and life is perfect now.
This is my problem. I can't let anything go. When baby L won't eat...I think it's my fault. When I can't get her in her crib, I feel, well, like a failure. I know I'm not, but I always feel that way. I'm always falling short of being the perfect mother...and if anyone dare calls me out for not having crumbs picked up or not having the front porch painted or not having my skirt drag the ground (seriously, it's happened), it's all over for me. It's grating on my need to be perfect, and falling short.
Yes, I understand no one is perfect. There is no supermom, duh. But how do I get these feelings to go away? How do I let someone tell me you're not doing that correctly and just shrug it off? How do I run out of time on my blog because I have a cranky baby and just say no big deal, I'll do it another day. Or what if I'm too tired to do a single thing more for the evening. How do I tell myself that's ok, without feeling guilty? As I write this, I feel guilty because there is laundry that needs folded.
I know most of these things can be changed with my mindset. Think happy thoughts, one of baby L's shirts reads. But after having a baby all day long to myself and a preschooler who is very temperamental these days, how do I change my mindset? Sounds so easy, but it's not.
Call me a hippie, but I had my placenta saved and encapsulated after baby L was born. I took the pills for the first month after she was born and saw lots of benefits. My milk came in quickly, my skin seemed fresh and most of all my mood was good a lot of the time. I still have some that I never took, and I plan to take some this week to test it out and see if they lift my spirits just a bit and maybe regulate my hormones ever so slightly. I'm surprised it's hit me at eight months out, but I guess hormones are a tricky thing.
I'll let you know how it all goes, but tell me. What has been your experience with your mood after birth, and how long afterwards did it change on you?