Another thing to do, is break down the four week rotation into weeks. This if you need a change you got lead way, you can move week 4 to week 2, or whatever. I generally use rotations as they really do help you keep a balanced exercise program. Something that generally gives you the best results and makes sure you don't skimp on one area that we tend to do, if we do a day by day thing. As we all have a certain likes in exercise. Some of us perfer cardio over strength training or vice vera, and sometimes even ignore stretching and how good it is for us, as it's boring, or doesn't feel like a workout, or whatever reason. (I'm not good at reaason for not stretching, as I love it.)
With a rotation it's on the schedule so your more likely to do it. If you miss a day or two of the rotation don't sweat it, just either pick up where you left off, if it's been more then one day missed is generally the better idea. Or start where you should be if you hadn't missed. There no foul, if you miss a day, just make it your rest day and get right back up again. And if it works for you, you can even do the rotation or week backwards, if that routine works better for your schedule that week, or even change the workouts around, just make sure you do the whole week.
I do this a lot with clients as some days, they don't have the energy, or one day is really stressful or they are really hyper, I simply just switch the rotation to fit there needs for the day, but make sure we get everything in that they need, for the whole week. Don't think in a rotation you got to do what it says on day to, if you don't feel like it, if day 4 fits your mood better that day, switch it, just make sure you do day 2 some time that week. Just make sure you don't work the same body part two days in a row. If that happens mix it up a bit more until you get a cardio or a stretch day in between the two.
HTH,
Kit