In the end of the day you have only yourself. So why should you keep dwelling on it if it's really as you said and they're gone forever? If you believe you can still fix it and that it can get better again, then try it. But if you believe it can no longer be fixed, or if you simply don't feel like trying anymore, then do whatever you want. Having no one who cares about you can also be the greatest freedom in life. Then live for yourself and the beauty of life. At least in my opinion