Charly,
sure to
I'm not sure to say goodbye.... means....It is not certain that I will say goodbye.
I'm sure to say goodbye....means......It is certain that I will say goodbye
-------This has an objective sense. It does not mean that 'I am confident that I will say goodbye', it means, IT is certain. Just another one of those odd things in the English language. ( A long time ago, it had the subjective meaning of, I am confident that I will say goodbye.)
sure about
I'm not sure about saying goodbye....means...I have doubts about saying goodbye. I'm not confident about saying goodbye.
I'm sure about saying goodbye....means....I am confident about saying goodbye. I am certain about saying goodbye.