I feel I want to self harm every time we end out skype calls.
Why would you harm yourself after our calls?
It helps me to focus before sleep interrupt my concentration.
You should seek mental help for your self harm. It is not good to harm yourself, a professional can help you with better coping mechanisms.
I will try to control myself next time.
I understand it can be a real struggle to learn new coping mechanisms. I think if you could talk to a neutral 3rd party you could really get some help.