It is very normal to have waterying eyes when you feel tired especially for the eyes. If you get tiredness from reading( especailly reading on monitor screen such as TV sets or computer etc), you are likely to feel burning eyes and watery eyes. In fact,this is not bad for the eyes, the tearing in your eyes can keep your moist and help you release from eyes strain.
Don't worry, It is a natural for the eyes react to tired. The more tear in your eyes is good to help you release from symptoms caused by eye strain such as burning eyes, dry eyes or red eyes. And what you shall do is to take a break. Keep your eyes for a while to allow your eyes relax. Besides, you can also massage the skin around the eyes to help relax your eye muscle.