The EFT reminder phrase is a simple, short statement used to help remain focused on the problem and prevent the mind from wandering. So in the example of a headache the reminder phrase would simply be 'This headache'.

In a more complicated pain with a long description such as, 'this sharp shooting pain up the side of my left leg whenever I try to bend over', you can either repeat the whole phrase, or abbreviate it. Simply shortening it to 'sharp shooting pain' will still work for most people, the important point is to remain focused on where you would feel the pain.