Emotions as a communication enabler or stopper

As I continue to think about what affects my communication skills and the reasons why I am not as good of a communicator as I should be, I realize that the effectiveness of my communications is heavily based on how I feel at a particular moment. If I have plenty of energy and if my day has gone well, I make more of an effort to communicate well. However if I am tired and it's close to the end of the day, then I tend to not communicate well if at all. Along the same line, if I am in a great mood and things are going well, I will make more of an effort to be more engaged. I know what I should say and how but sometimes I just chose not to, for reasons that I nothing to do with my communication skills. I guess it is better to not do the right thing and know about it than not do the right thing and not have a clue.