You've just described my last two months of shooting. I'll be the first to admit that I've never been a spectacular shooter. Probably average around a 22. So if I can put up a 23, 24 or even the occasional 25 that's a good day for me. And if I shoot a 19 or a 20 I consider it a bad round. But this summer I've shot a 15, immediately followed by a 23. Managed a couple of 24's. But on the other end I actually shot a 13 which is the worst score I've had since I started shooting 6 years ago (although admittedly I was so p*ss*d off I kind of gave up after the first 15 targets). For me, it just starts getting in my head. Miss a target. Then drop the next target. Now I start thinking about what I'm doing wrong. Start aiming or hesitating before I pull the trigger. That's two more lost. Or I'm on 5 and I get a hard right and shoot behind it. The next target is, of course, another hard right so I overcompensate and end up leading it by 5 feet. Another miss.
The best trap shooter I know (someone who regularly competes in state and regional tournaments and usually comes away with a win in at least one event) once told me that the best trap shooters either have almost nothing going on between their two ears or are very smart and use their smarts to overcome any mental doubts. (He obviously believed he fell into the second category). Probably something to this.