Also if you are going to Irish up your coffee, do it with a proper Irish whiskey like Tullamore Dew or Jameson. JD has nothing on either of them (my preference is TD).
Too much coffee can cause serious problems with health. One of the most common is anxiety. It will deplete your serotonin levels, and give you issues you never thought were possible. I know this very well as I was once a coffee addict.