Hold up: To slow something's progress ("What's holding up traffic?") or to rob ("he was arrested for holding up the bank.") To not be fatigued ("You've been running for an hour, how are you holding up?)
Hold out: To stay together/in ("If we can hold out just a little longer, we'll win the race.") To offer ("Hold out your hand.")
Hold off: To wait or do something later ("let's hold off on buying the house until we have better credit")
A. It's raining. I think we should hold off the meeting.
B. The bar is really heavy. Are you sure you can hold up any longer?
C. I think we have to hold off a little longer untill we are ready to really commit to each other.
D. a: I can live two days without water. b: I don't think I can hold out/hold up that long.
E. Sorry, I got held up by the heavy traffic.
So one day I decided to break it down to her.
In this context, "break it down" means to make the information easier to understand, break it into smaller pieces.
B: Singing makes people feel good. It makes you break down who you are and (vent your feeling out.?)
Doesn't really work here. Maybe use "come out of your shell" (be less shy)