Self-sufficiency becomes isolation when needing nobody becomes part of identity.

Needing nobody is a fine practical skill and a poor identity. Once it becomes who you are, every offer of help reads as a threat to that identity, so you decline things you would benefit from and slowly narrow the number of people who are close enough to offer. The competence stays and the connection thins, and the second loss is much harder to notice.

Notice whether you say no to help automatically, before considering it. Try accepting one offer without qualifying it or immediately repaying it. Letting someone do something for you is a form of intimacy, and refusing it is not neutral.