I'm positive 
~> I'm positive.

I have a opinion.
~> I have an opinion.

I'm exiting.
~> I'm excited.

REMINDERS:
* Don't forget to end your sentence with a period (.). 
* We used article AN for non-particular nouns that start with a vowel sound.
* Exciting is used to describe something that makes you feel excited. Excited is used to describe what you feel.