If you're using the keyboard, don't focus on the actual letters that pop up. They'll be one of the four movement buttons (WASD), and each will show up on a different part of the screen. W will always pop up on the top, A will always be on the left, D will always be on the right, and S will always be on the bottom. If you avoid focusing on anything specific and take the whole screen in, it should become much easier to see which direction is popping up and react in time.