Hey man you're not alone...
In fact I experienced something like this a few days ago.
In my previous lesson we'd been up in the pattern. Things went very well (this was third lesson doing pattern work). Things went so well in fact that my instructor feels that I'm ready to solo. So the next lesson rolls around and we get into the pattern and this time ATC tells us to use right traffic this time. No problem I think, even though all my practice to this point has been left traffic. Boy oh boy was I wrong. As I turn crosswind I suddenly forget how to do a coordinated turn. My brain eventually kicks in and I hit the rudder.
I land for the first T&G and then suddenly I'm flying sideways off the runway (no wind that day...amazing I know). *sigh* at least the landing was smooth....of course I touched down with all 3 wheels at once which wasn't good, but I did smash the nose wheel.
Anyhow, I know what you mean, but I can say this: after that crappy T&G things got a lot better. I just thought about the whole process as I was doing it. I even started talking through the steps you know, like, "Okay, at pattern alt - 500' so lets turn right, make sure you're coordinated, look outside..." etc. In the end that rest of my landings were quite good (although I gotta remember to keep my airspeed up on final), and I made all my radio calls (which is something for me, prior to that point I was letting the airplane get ahead of me and my CFI made the calls for me, so I could...um...fly). IMHO, we're learning a new skill here and I find that for me it's when things start feeling "automatic" that things start going downhill. I just concentrate as if I'm doing this for the first time and things fall back into place. Like my CFI says, "it's the magic of repetition".
Keep the faith.
Naunga