When you are feeling sleepy, there are some signs that will reflect. Your eyes become dull and heavy, you become quiet, and your body becomes inactive, feeling sluggish and drowsy. Sleep is meant to put the body and its systems at rest in order to gain back strength. You may sleep when your body is tired and needs rest, or when the environment is conducive to sleep. The amazing thing about sleep is that it does not only have an effect on your body but also on your mental health.
Likewise, tiredness has an effect on both your physical and mental faculties. Just that, on the other hand, tiredness comes about when the body is exhausted or has exhausted a lot of strength and energy. When you are tired, stress and depression come in, and it tends to affect your emotions and dispositions also. A tired person loses interest in whatever he is doing. Being underweight or overweight can also easily cause tiredness, and might be due to medical effects sometimes.