It's easy to turn an active rest day into just another training day, but you should avoid doing so at all costs. A two hour ride in your endurance zone is not active rest. If you are tired, get some sleep, take a kick-back day, or whatever it takes not to feel tired. When you don't feel sleepy anymore, you can try some active rest like a <30 minute easy (actually easy, not should be easy) cruise on the bike, or personally, I like to mix it up with other recreational activities like a walk or swim, again keep it leisurely and fun, remember this is just to keep the blood flowing and your muscles limber.