When driving, you need to have your full attention on the road and on your surroundings, for your safety and the safety of others. Strong emotions not only take your attention away from driving, but they also affect your decision-making skills and keep you from judging and reasoning accurately. Driving while affected by strong emotions can be just as dangerous as driving while drowsy or drunk, you will be distracted by other things and not have the right mindset to drive.
Hope this helps! :)