Loneliness can take hold gradually, almost without you noticing, until it feels like a permanent state rather than a passing one. Sometimes it comes from a specific shift: a move, the end of a relationship, a period of depression or social anxiety. Sometimes there's no clear cause, and that makes it harder to talk about. Either way, the gap between where you are and where you want to be socially can feel enormous.
Working with a therapist on isolation usually starts with what's actually getting in the way. If social anxiety is part of the picture, you'd work on the specific patterns of thought and avoidance that keep you stuck. If the issue is more about connection quality than quantity, the focus goes there instead. Gradually building more engagement, at a pace that doesn't overwhelm you, tends to be more effective than pushing yourself into situations before you're ready.