I met up with a known friend about lots of topics and drove him home.
I got to talk about my plans on what to study at university. I also mentioned an idea I have for a startup, yet presented it as if I'm planning to create that startup. He asked me what's the startup idea. I hesitated, and then told him the idea.
I'm now anxious because I revealed a "secret" and am anxious that he'll spread the word through casual chat and I will lose the opportunity.
It's an idea for an app I just had visionary thoughts about, nothing more.

I got anxious because I presented the startup as if I'm working on it (overstatement?) and have an anxiety of revealing info due to competition, even if he's a friend.

I'm kinda sure I'm exaggerating, but I need reassurance, or whatever else you think.