Tied up

A person who is 'tied up' is busy and can't take on a new request from someone else. It can also be used as an apology to say that they couldn't get to something they were supposed to be doing because something unexpected happened to prevent them from doing it. To add emphasis, they can say they're 'all tied up.' this expression is often used in a work place or other professional environment.

Example:
-I'm sorry; I can't help you with that. I'm all tied up today with a project. Maybe tomorrow?
-Sounds good.

-Did you finish the Stevens case?
-No, I'm sorry. I was all tied up in meetings with my team and never got around to it.

Me and my big mouth!

You say 'Me and my big mouth' when you're embarrassed about telling someone something that was supposed to be a secret.

Example:
-I can't believe you told Sarah about her surprise party!
-Me and my big mouth! I'm really sorry!

*Just*

'*Just*' when used with a little pause and emphasis after it means that someone has, moments ago, completed an activity. Sometimes it can also be said a little slower to be used as an indirect apology to someone when a person has finally done something that was supposed to have been done earlier.

Examples:
-I *just* texted you their phone number!

(Running late, talking on the phone). -He *just* finished his nap and we're on our way out the door now!

Completely

'Completely' is used as a way to apologize for something that was done by accident that a person is embarrassed about.

Examples:
-I'm so sorry I missed class! I went home after my first class and completely fell asleep!

-I can't believe I didn't call you on your birthday! I completely forgot!

Just sayin'

"Just sayin'" is a conversation ender used by people as a way to get the last word in a conversation. As it uses 'just,' it also can be almost be seen as a sort of apology for the previous statements, which were likely strong and opinionated.

-Do you want to go to Alex's party now?
-No! I *don't* want to go to to his party because he's a total jerk. Just sayin'!

Shutting up now...

"Shutting up now..." is an expression speakers of American English use to show embarrassment and apologize when they realize they've been monopolizing the conversation and not giving the other person a chance to respond.

Example:
-(yawns)
-Ok, shutting up now!