How do I know if I am working out too hard, or pushing myself too much, is there a way to monitor this? 

Again, if you learn to listen to your body’s signals you will know when you are working out too hard or too intensely. But if you prefer to know more accurately what your heart rate is, so as to keep it in the moderate-intense range, you can purchase a heart rate watch that will tell you where you are at. Your heart rate should be between 50 to 70% of your maximum heart rate for a moderate-intense workout. Your maximum heart rate is based on your age. An estimate of your maximum age-related heart rate can be obtained by subtracting your age from 220.