Steaks start out almost perfect, especially when you purchase a good steak. One rule about the way steaks cook is that the fat will shrink faster than the meat. This can cause the fat to fold or compress the meat. This pressure can squeeze out the juices and make the steak more difficult to eat. So, occasionally you might to trim a steak to make it cook better. This will also reduce the risk of flare-ups by reducing the amount of fat. Of course, the fat is important to the flavor of a steak so it best not to cut it all off.
Here we have a nice New York Strip. This steak has a nice thick strip of fat running down one side. This strip of fat is too thick to really benefit the steak. Of course, you could leave it alone, but it would benefit your heart health and the outcome of the cooked steak if it is trimmed first. Remember that this strip of fat is going to shrink a lot more than the meat, so you need to break it up a bit.