I'm currently running four days/week: Monday, Tuesday, Wednesday, Saturday. That gives me two rest days before my long run, speed training, or hills on Saturday. I look forward to and enjoy these rest days, because they help insure that I'm well rested and have a high energy level for Saturday. Sunday is also a rest day because that is my Sabbath, and that day helps insure that I'm well rested for my Monday, Tuesday, and Wednesday runs. Without sufficient rest, I would not be able to perform at a high level, and I wouldn't enjoy my runs as much as I do. My body needs rest as well as exercise.
Many runners have a problem with rest days. They are either so enthused about their running that they miss running on those days, or they have the misconception that their performance will deteriorate if they miss even one day of running. They don't seem to realize that our bodies react slowly -- slowly to improvements and slowly to degradations, and that one or two days without running will have little effect on their condition. Also, many of them are typical type A persons who are driven to compete with everything in life, and they have a hard time when they aren't in competition with something. Instead of a rest day, many runners get rest by doing a shorter, slower rest run. In fact, that is the basis for my Monday and Tuesday runs. They are about half the distance of my other two runs. So, I do rest runs and also take rest days. If a person listens to their body, they can decide on the best way to get rest.
So, good morning rest days! You're welcome in my life!