lucky

[dido4]

Which is better to express that I am so lucky to win the prize?
1.I am the lucky dog.
2.I am a lucky dog.

THank you

[Mister Micawber]

.
It depends on context, Dido:

MrA: Who's the lucky dog who won the lottery?
MsB: I'm the lucky dog-- I did!


MrC: Guess what?-- I'm a lucky dog!
MsD: Why?
MrC: I won the lottery!
.