Out of the Blue

Unexpectedly, without warning

Sophisticated

Having refined taste, knowledge, or experience of the world

Cry over Spilt Milk

To be upset about something that has already happened and cannot be changed

Strike While the Iron Is Hot

To act at the right moment when circumstances are favorable

Storm in a Teacup

A lot of commotion or fuss about a trivial matter

Steal Someone's Heart

To cause someone to fall in love with you