Is it normal to have light green vaginal discharge? sometimes, when i lack of enough rest, there will be more of this discharge? what should i do?

Discharge: I would get evaluated for infection. One of the potential causes of greenish discharge is gonorrhea, though other infections can cause the same color.

No it is not: You may have chronic vaginitis / vaginosis. It is indeed flaring up when you overworked, exhausted with over-restrictive diet, etc. And your body immune system function is diminishing. You do need examination by your doctor, some lab work to establish diagnosis; you also need to review and possibly change your daily routine to make it healthier.