There are so many benefits to Cardio exercise. Getting regular exercise such as running and cycling can help improve the health of our heart, build better endurance and may prevent certain diseases. However, just like anything else in life, doing something in excess can cause issues. For instance cardiovascular exercise puts stress on our hearts. So in moderation it will strengthen the heart muscle, but in excess cardiovascular exercise can weaken it. The body needs a chance to rest and recover.
Some of the issues excess cardio can cause are injuries, trouble sleeping (due to increased cortisol levels), losing muscle mass which can lead to a slower metabolism and feeling depleted or wiped out just to name a few. So give your body a rest from cardio or try replacing some of your cardio days with strength training. Not only will this give your body the chance to recover from the physical stress on your body but you will strengthen your muscles and support your joints decreasing the risk of future injury.