I agree with Mark.
AIkido is an interesting art. You can master the techniques and skills and cognitively know them cold, yet some days, weeks, or months you just can't seem to quite be in the zone.
I was suprised several years ago when I took off about a year and a half and came back cold into a big seminar how well my aikido improved during that year and a half. While I had been into meditation, had worked on alot of mental aspects of budo, I had not praticed aikido for that time.
I was in the zone and in my game! It was amazing how relaxed and how everything flowed.
That ended a few weeks later it seemed as I picked apart my technique and got back into trying to "get better".
I attribute a great deal of what happens to the mental and emotional aspects.
As a 5th Kyu, you are probably experiencing all this at once. Sometimes you are good and master the techniques, then WOW! you are hot, then all of a sudden you just can't seem to get it right for whatever reason!
I think we all experience this from time to time. I think higher ranking students are able to "shorten this cycle" more as they develop themselves in all three realms of mental, physical, and spirtual. (at least I hope that is the case!)