How to stop being so open

So I don’t know if anyone else feels like this, I feel like I’m alone here.

I don’t know how to stop being so open with everyone about everything. I’ve always been an outgoing person my entire life. Was never the shy kid. Made friends easily. So I feel like that’s carried into my adulthood and I go around thinking everyone has my back and I’m very open with almost everything in my life. If I need to vent, I find the closest person to me at that moment type thing. I also don’t really wait to say things, for instance, just went through a break up and told a bunch of people that the reason we broke up was because of a completely wrong reason because I hadn’t had all the information yet. Idk why I get so anxious or what my mind is trying to process by doing this but I would really appreciate people’s help. It’s a major flaw.

I just want to learn how to be more private with things and realize not everyone needs to know what I’m doing.