Only take a week completely off the bike if you want to start losing fitness.
If you felt like you were tired and needed a break from your regular training, you should maintain the intensity you usually ride at and reduce the volume of training by up to 40%.
Usually, for many people who aren't pro cyclists and have other things to do (e.g., family, work, school, etc) these normal life stressors get in the way of training sufficiently to give the rider a natural recovery period of a day or two.
FWIW, i usually train/ride 6 or 7 days a week with one or two of those rides being a real easy recovery spin. If i feel tired one week, i may have an extra day off or an additional day or two.
There's no real need to schedule a rest week, every 4th week (and even if you did, you don't want to do nothing for that week).
Ric