Don't feel bad. I was working on a certain sweater that Shall Not Be Named, and it was giving me a lot of trouble. I have done plenty of sweaters, but this one was Pure Evil.
I took a lesson to fix it, and the mistakes I had made were "hiding in plain sight". I had been working with the sweater so long, I never would have seen them myself, even after letting the thing sit in the corner by itself for a few weeks to think about what it had done wrong (more than once).
The cool part was that I learned a lot just by watching the teacher do "forensics" on my sweater - she basically had to dissect the neckline to find out what killed it! Plus, I got a lot of confidence from the experience.I had half expected her to say, "Maybe you'd like to go back to making scarves for a while".
DPNs are the strangest things anyway. The first time I used them I had zero problem and made two cell phone holders in a flash. Then six months later I picked them up again and god help me I couldn't get it. At one point I found myself knitting on the INSIDE of my project. And every time I would try to pull the work right side out, I would somehow STILL be working on the inside. I frogged and started over, and within a few inches, I was on the inside AGAIN.
Right now I am working on this http://cache.lionbrand.com/patterns/1190AD.html
which I have to brag about because it is both beautiful (so I want to finish) and killing me slowly. I am on the third color and I keep goofing up somewhere that requires me to keep redoing that third color. Tonight might be the night ladies and gentlemen. Point is, it starts with 8sts on DPNs, then you k2, M1 for the first round, k3, M1 for the third round, etc.
I was CERTAIN that I had twisted my sts and undid it I can't tell you how many times. Finally I just kept going even though I was sure it was ruined and wouldn't work, but at a certain point it got big enough for me to tell that it was fine. Of course, as soon as I get through the 3rd color, I get to swap out to a short circs, and I can hardly wait (which may be why I keep sabotoging that third color and having to frog back).
DH is famous for saying "you aren't born with the knowledge". I love that saying! (though if you ask me, he WAS born knowing math and that just isn't fair!) We do this for fun, and at a certain point struggling with something that you are absolutely capable of isn't fun. So you find someone to help you over the hump and you are smooth sailing for a longtime afterwards.