In seventh heaven
Definition 1 of 1
Pro Tip 1/3Extreme Joy
Use it to describe a state of extreme happiness, like achieving a dream. 
When he won the lottery, he was in seventh heaven.
Pro Tip 2/3Positive Events
Best used when something very good happens unexpectedly or as a wish fulfillment. 
She was in seventh heaven when she found her lost puppy.
Pro Tip 3/3Informal
It's informal, so it's best for casual conversations, not in formal writing or speeches. 
I was in seventh heaven at the surprise birthday party.