(to be) like a dog with two tails phrase informal
The phrase alludes to the belief that a dog wags its tail as a sign of pleasure or happiness.
To be very happy and excited about something
When my nephew received a new lego box, he was like a dog with two tails.
My friend has been like a dog with two tails since she got accepted to Harvard.
She will be like a dog with two tails if we hold a surprise birthday party for her.
To make someone feel more confident or happy, especially when they thought that they can't achieve what they want
Happy or cheerful; in a good mood
To smile broadly