“You must be ecstatic!”

You're having an after-work drink with a colleague. She tells you that she recently became a grandmother for the first time. You can see that she's excited about it. You say:

You must be ecstatic!

You must (be/have/do something)

Use this expression when you want to make a guess about someone. It's really useful when you're trying to guess what someone is feeling. For example:

You must be so excited!

You must feel quite a sense of accomplishment.

(someone) is ecstatic

"Ecstatic" means really, really happy. Things that might make a person "ecstatic" include:

• winning the lottery
• getting an amazing job
• getting engaged

"Ecstatic" is an "ungradable" adjective. It's similar to these:

Man, I am so exhausted!

I've been having excruciating sinus headaches for the last few days.

Oh my God, that's horrible!

Adjectives like these shouldn't be used with adverbs like "very" or "a little". That's because "very" is already included in the meaning of the word.