Reading that you all have that kind of bad days too is kind of comforting. So I'm not the only one who fucks up simple ollies.
My problem is that I adopted a wrong posture (tilting my right hip forward) a long time ago. This really fucks up my core, thus my balance, and ultimately my ability to skate.
I've been doing physical therapy for quite some time now and been getting much better, but after work or when I had a long session on a previous day, my core muscles get weak and I slump back into the wrong posture.
Then I really feel like shit and mostly just extremely insecure. I know that I have the ability to ollie up the curb, but I just can't, because I feel I can't control my body.
Usually I stick to very basic stuff then (all kinds of 180s, basic lip tricks on quarters and goofing around) and have fun anyway, but when I've had a couple of bad days in a row, it bums me out, because there's no progression.