IWTL how to learn how to love being alone if my former friends have either abandoned me or if they're busy with their partners

Right now, I've been having thoughts of fictional characters from either movies or TV shows being busy with their partners and not having time for their friends. I used to have friends from high school in the past. Now they've either drifted away because of some misunderstandings or that they could be busy with their own partners.

These two things made me feel like I shouldn't worry about them and I want to focus on my hobbies, like my writing, and enjoy doing it alone. I could even find other hobbies that I might enjoy as much as I want without caring about what people think or my former friends. But it's hard to do things alone when I'm still thinking about them. Tell me, how do I enjoy being alone with no worries or troubling thoughts?