Variety may be the spice of life, but there's something to be said for having well established routines as well. Sticking to a training routine is important for several reasons.
First, people tend to have habitual inertia. By that, I mean that we're more likely to keep doing the things that we're already doing. If you are going to the dojo/gym three times a week for several months, you'll likely continue that. However, if you go on vacation and miss a whole week of training, not only has your body lost a step in terms of conditioning but you are also mentally less motivated to get back into your routine. I find this particularly true of any routine that is difficult either mentally or physically. It's just like going back to school after summer break. It's painful at first, but if you force yourself you can get back into the swing of things.
As mentioned above, stepping out of your routine will result in a quick degradation of whatever physical gains you've achieved. As the saying goes, "use it or lose it". This step backwards actually makes returning to the routine harder for many people because of the feeling of wasted time and effort. And besides, do you know what's easier than going to the dojo? Watching TV. The TV never kicked you in the gut or hyperextended your arm (at least I hope not...otherwise you might be doin' it wrong). The longer you are out of your difficult routine (training) the more entrenched you will get in your easy routine (leisure).
To paraphrase a quote from Tim Ferriss, you should guard against the weaknesses of your lesser self. That means that if you know that breaking your routine will result in a downward spiral of behavior, then do everything you can to maintain that routine. A good tip is to never miss two days (or classes) in a row. Missing one day is just a slip up, but twice in a row is on its way to becoming a new habit.
In martial arts, we train to know ourselves better. So take an honest look and figure out a way to stick with the training that you know is good for you!