Some people frequently ignore the messages their bodies are trying to tell them, but others who honor their body's requests will benefit from doing so. Being in tune with your body is an important skill to develop. It's like noticing the gauges on your dashboard. Some people have even turned it into an art form. I once heard of an NFL receiver who was so in tune with his body that he could instinctively tell when his body fat percentage fluctuated by less than 1%.
Listening to your body may include things like taking a break from a workout when your "spidey senses" tell you to do so even though you've had it planned all week. WARNING: Don't use this principle to cop-out when you are just too lazy to exercise. There is a difference between simple laziness and listening to subtle clues that your body is giving you to take it easy or rest.
Nutrition is another area where this principle comes into play. Years ago I heard a woman speak who had struggled with her weight her entire life. She said the moment that really turned things around for her was when she decided to focus on enjoying her food and tried to listen to feedback from her body while she ate. She previously ate large quantities of food and never felt full, but now she sits down and takes time to really enjoy her food. She listens to when her body tells her she's satisfied and that has helped her maintain a healthy weight for years without dieting or having to avoid the traditional culprit foods.
I'm intrigued with the concept of tuning in and listening to the subtle clues your body is trying to tell you. There are times when I feel my body is begging me for a salad or steamed vegetables and it's almost like it's requesting an antidote to some kind of poison I've eaten. Other times you might feel that you are coming down with something so resting and taking undue stress off your body is the best option.
One of the reasons I like yoga, stretching, meditating, and deep breathing is because these activities offer insightful feedback and cause you to listen to your body. This can help you know when it is safe to really push yourself and when you should take things a little easier. I also believe it's beneficial to view your body as an ally rather than an enemy you are always fighting against. When you are no longer at odds with your body, but rather in harmony with it, you will be surprised at the positive changes you can make.