Nobody tells you this part. The part where getting better at your life, more serious about who you're becoming, clearer about what you want, quietly ends friendships that used to feel permanent.
It doesn't happen dramatically. There's rarely a falling out. It's more like a slow and mutual incomprehension. You're interested in different things. The old conversations feel thin. You reach out less. They reach out less. At some point you realize you're remembering the friendship more than you're having it.
This is not a failure. It's the cost of growth, and it's a cost worth paying, but it's still a cost. And if nobody told you about it, the loneliness of that transition can feel like something is wrong with you.
Nothing is wrong with you.
Relationships are mostly proximity and shared context. School puts you in a room with the same people for years, and what gets called friendship is often just proximity made comfortable over time. When the proximity ends and the shared context changes, many of those connections don't survive. Not because anyone was a bad friend. Because the relationship was built on a context that no longer exists.
The people who survive your growth are a different kind. They're not comfortable because you've been together a long time. They're interesting because of what they're building. The conversations don't age. There's no performance required.
You find them later than you'd like and you keep them differently than the old ones.