I was introverted as a kid mostly because I was shy. Today, I am more of an ambivert. I like being with people but also enjoy my own company. I used to brood a lot and regurgitate past grievances. Focusing on others has helped to pull me out of a morass of self-pity and resentment.
I still don’t enjoy large parties or “working the room.” But I found some ways of getting around this. Either by helping someone or by participating in or organizing group activities that interest both me and my friends. I am absolutely terrible at small talk, I get around this problem by talking to people about shared interests.
Being completely selfish here, but focusing on others has helped me.