A goodbye is a small summary of everything: what happened, what it was like, where you are now, and what comes next.

Looking…	Tense	Example
back, at a finished period	perfeito	Foi um ano inesquecível. — It was an unforgettable year.
back, at how things were	imperfeito	Quando eu cheguei, eu não falava português. — When I arrived, I didn't speak Portuguese.
at today	present	Hoje eu falo português! — Today I speak Portuguese!
ahead	ir + infinitive	Eu vou voltar. — I'm going to come back.

A few words for the occasion:

• inesquecível — unforgettable
• agradecer por — to thank for: Quero agradecer por tudo.
• prometer — to promise: Eu prometo que vou voltar.
• chorar — to cry
• ir embora — to leave, to go away: Ela vai embora amanhã.