Time is both your friend and your enemy. Gently placing a great cut of meat on the grill and having the patience to leave it alone while it sizzles and chars to perfection on each side is a learned skill bordering on art. But after the cooking - time becomes a taskmaster.
Leave meat to sit after coming off the heat for at least 10 minutes. Let the muscles rest and all the fluids recombine. The cooking is not complete until food rests for a few moments after coming off the heat in order for the flavors to settle and the food to stabilize. Temperature is your friend at this stage. Taking the food off the cooking surface when it is just reaching the "fully cooked" temperature requires a thermometer. Time and temperature are your friends at this stage. Knowing you have an exact temperature, and leaving food on the cooking surface for just the right time gives you incredible control in seasoning at the right time to draw out just the right flavors.
As a reminder, the temperature at which a particular meat is 'fully cooked' is shown:
At the fully cooked stage, bacteria and other undesirable additions will start to attach to the food surface. At 135-degrees, they can grow and the number of active cells can double every 20 minutes. From that calculation - you can see it won't take long for a wonderful meal to turn into an emergency room visit. In fact - after 4 hours between 135 and 70 degrees, you should throw the food out because it just may not be safe. Of course - if you can keep the food warm it will stay safe longer. If it can be chilled - get it below 40 degrees within a couple of hours and it will inhibit growth of the nasties too.
Here again, time and temperature can be your friends. Knowing that you have some small amount of time with your BBQ to get it to the table and start consumption gives you a bit of leeway to plan when things can come off the grill and rest, while other things go on to finish up. Bringing it all to the table while it is safe is, after all, what the grilling season is all about.
So use your time wisely. Let things rest appropriately. Get a probe thermometer and use it so that you KNOW when meats are safe to eat.
Eat Healthy. Eat Often.