Why is it self-absorbed for someone to include themselves in the conversation, but it's not self-absorbed for you to come up to me and talk to me about your guitar playing?

You can come up to me and say, "Hey, guess what!? I just started playing guitar!" And I can't say, "No kidding? My mom just started playing guitar, too!" or, "No way! I just started drumming a few weeks ago. Maybe we can jam soon?"

How is my response "self-absorbed" but you starting a conversation about yourself isn't?

If you start the conversation, I'm just supposed to keep asking you questions about your experience until you're done talking about it?

I mean, if we're friends, shouldn't you care about what I think is relevant as much as I should care about what you think is relevant?

And anyway, if you _really_ want to talk about how it's going - can't you just take the conversation there?

I understand if you say something like, "Nice. I've always wanted to learn to play, and I never thought I could, and already I've learned so much, and I'm getting close to being able to play my favorite song."

And I say, "Oh, cool. Hopefully you can play my favorite song next. But it's really hard, you'll probably need a few years. You know, I used to be friends with Kurt Cobain's assistant, right? That's how I got into music in the first place....."

^ That seems self-absorbed. The first seems like genuine conversation.