I've been bummed before. I ended up 'taking a break' for about a two weeks, and quickly rediscovered why I love going to the dojo and training. Basically I go nuts if I don't train and get rid of excess energy and stress. I just wasn't built for sitting around doing silly junk all day.
Absence makes the heart grow fonder.

But watch out, 'breaks' have a tendency to turn into 'quits'.
Sometimes absence makes the heart go wander.

But face it, you like pain, struggle, and triumph. So you'll come back. Just keep in mind how lame you are for taking a break, and how you'll feel when you're too old to do Aikido, sitting there in the retirement home, wishing you had been more intense when you were younger, hoping some one will invent a time machine so you can go back, kick your younger self in the ass and say "SHOW YOUR ENERGY!!!!!!!!!".

I would say that it is, like most things, different for everyone. My work forces me to train sporadically (Sometimes I can do many times a week, sometimes none). I think that this helps keep from getting burned out on it. I find that I miss it when I don't go, for a variety of reasons.

I did take a long break, about 10 years (I try not to think about how far I would have come in that time if I had been training). During that time, it never really left my thoughts as I continually looked forward to when I would be able to start back. Of course, this particular break was more about life events than burn out, but I think the parallel holds. If you truly love doing it, you'll find your way back to it one way or another.

one week a couple years ago I mentioned to one older guy (~30 years of training or so) that I was having one of those weeks where I didn't want to come and had no energy, and he said "Oh, I've had whole years like that."

it's a normal part of training, and I think training in anything, and yeah, you just slog through it. at some point a year or so ago, I wasn't feeling like I was doing techniques well, so I stopped trying so hard on techniques (since it seemed a lost cause for the moment) and worked on ukemi instead. so you can alter the focus of your training and see if that makes a difference.

nothing says you have to train *hard*, also, and there's a useful separation between the amount of force involved, and your level of intensity: one thing we work hard to teach beginners is that "intense" doesn't mean "fast". hopefully you have a dojo where you can train at a pace that works for you.

and finally, the slow spots are a time to think about whether you're really enjoying it, and whether it's something you want to continue doing. I know for me, I resist going to the dojo (even during the easy times of my training, because I'm lazy), and every time I go and have a wonderful time. and that's been consistent for over four years now.

you're not lame just for taking a break, but understand why you're taking it: if it's because you genuinely don't want to do aikido, or if you're just avoiding it because you feel your progress is slow and that's not as shiny and satisfying as it sometimes is. if the latter, think about why you're training, what you hope to gain from it, and what you might learn by continuing your training even in the absence of immediately perceptible progress.

If someone never had a less than enthusiastic day towards whatever endeavor is important to them I would suspect liberal use of good drugs, and would be tempted to ask what they were.

Intensity and passion toward an activity are not always easy to maintain. For myself, when I feel less than enthusiastic about trainiong I just go anyways. I have a schedule of classes I attend, once per day Monday through Friday, and unless I have a physical ailment or a familial obligation, I show up. I don't indulge in the luxury of asking why I do Aikido very often. I just know it is good for me, and I keep showing up.

I have seen others take breaks, and that seems to work for them. It doesn't for me. I don't think I am ever going to get very good at Aikido, but I do know the only way I will get better is to train.

I think this is:

1) Very typical, I personally experienced it (and failed to follow the advice I'm about to give below - LAME!)

2) Chances are you sensei/sempai aren't going to push you (it's not like Tae Kwan Do where everyone will give you crap for not being on the mat) which leads to this:

My advice is to push through it and train anyway, even if you're not very happy with the quality of your energy/technique. I think "pushing through" this particular frustration, like many of the other frustrations of training, is part of it.