It's hard to be alone, I know this pretty well, since I've been afraid to stay alone for the most part of my life. It's hard to stay calm when someone is mad at you, cos you are afraid he or she will leave you. So you try to do anything to prevent it from happening by crying or pretending you are happy even when you are not. How many times did this happen to you? Many? Than I am talking to you... I don't know many way to help in this situation, but I kind of working on some methods to help me get rid of this fear of being left and staying alone:
I am trying to spend time with myself as much as I can. I learn this from asian teaching that I am currently into. It was really hard to start but now it's getting better and better. I started to go to eat somewhere alone, to go shopping, trying to have fun with myself. In the beginning all I had was a pity to myself, which made my fear only worse, but over some time I felt that some changes were happening in my heart, like this pity was gone. Now when I stay alone, I don't feel lonely anymore, as I used to. Don't be afraid to stay alone with yourself, read a book or just listen to music. Some people are so busy all the time that they don't hear their own inner voice that needs to be heard.
Always remember about the people that love you. Many times staying alone we forget about those who love us but for some reasons can't be with us at the certain moment. We blame them for leaving us alone. When I was a kid, my older sister left to the US, which is REALLY far away from Russia. Since she has always been my best friend, I felt betrayed and left alone. Later on I got this feeling of anger which brought me pretty far from my sister for many years. Only now I realize that she still loves me even though she left than. To me it's hard to understand still, but I don't have anger anymore, cos I learnt to see good things she does for me, which prove her love for me. If the person is not with you all the time, doesn't mean he doesn't love you, the only way to be cool with it is to accept this life as it is. People come and leave, they have their own business, their own problems and lives, but you stay with yourself no matter what. You are your own best friend.
It's cool to express your feelings and thoughts on a paper. When I feel lonely I sometimes write my feelings down, I know that this moment of loneliness was given me for a reason. And the reason is to understand myself better, to listen to my own mind and soul in order to find peace.
Every single day is given to us to develop, improve and grow. Don't let depression break you. Always remember, you are not alone. There are so many people just like we are, who can feel the same way as we do, and we are here to support, to help and love each other.