I don't have any answers, but man, I know what you mean! There are times when I feel I know nothing about painting, or about art, or about much of anything for that matter. I get really upset, too and wonder if there is any point in picking up a brush again.
Then I am grumpy, and I can't even seem to enjoy a good meal. And my poor family that has to put up with me...
Now, I'd like to think that this is all part of the process of learning and growing. There were times when I struggled like this, and afterwards made great strides. But not always!
So, I would be glad to hear what others do to tame the madness! And maybe, at least, you will feel better that you are not the only one who ends up wrecking paintings again and again and gets no where and feels miserable? (Did you see my thread with the bridal portrait profile!?!)
OK, sorry, not my thread to rant.