Rest days: Try to rest a minimum of 2 days a week or 1rest day after 3 days work. You may think about taking 3 rest days every few months and a week every several months. Listen to your body. If you are constantly sore, performance is not improving or you are actually decreasing you may need to take a day or 2 or 3 off. If you deside to do a 2 a day, it should in most cases be followed up by a rest day. You feel you must come to the gym try an active recovery day. Remember we get stronger not when we workout but when we rest.
Active Recovery: Getting that blood flowing, even at extremely low levels of intensity, can enhance and speed recovery, and even eliminate DOMS (delayed onset muscle soreness). Ever hit a WOD hard, then jump in your car and drive home and lay on the couch for 2 hours? Remember how sore you were? Active recovery can eliminate that. This can entail anything from therapeutic massage to foam rolling/mobility work to an easy 2k row. Try a restorative/athlete yoga class or come into the gym and do some oly skill with a little bar or PVC pipe. You’ll recover faster and become a better athlete.
A great blog for rest day mobility work ideas is MobilityWOD