My mother is the only one I have any kind of relationship with, and it has been rocky more often than not.
That's quite common, unfortunately. Just remember even our parents aren't perfect (duh), and they have their own personal struggles too. The fact that she has a relationship with you still proves that she cares about you, even if at times her attitude might not say the same at times.
I'm not trying to say I know your situation or anything, but if someone leaves you they don't deserve you, so you shouldn't care about them IMO. You shouldn't be afraid to get close to people, or hold those you care about close and show them that you care about them too.
There is happiness to be found from others, whether it be a friend, a family member, a pet, a neighbor, a love interest, a random smiling saying hello, or asking how your day has been, or someone online on a forum. We aren't built to live a solitary life, even if for some we prefer being alone more than others. It's much easier to build yourself up when you have others around you, and although there are people in this world who are negative and don't like you, they are the minority. As long as you put yourself out there, there will be someone who is willing to smile and care about you.