Growing up and saying goodbye to more and more things.

This is a sentence fragment, but, I don't know if you intended it thus.

If you are writing in an informal way to show your thinking, this is fine. Natives do this--write sentence fragments deliberately to use the style of spoken English, for stylistic purposes.

If you intended this to be a complete sentence, as would normally be used in formal writing, then it could be one of these, depending what you want to say:

I'm growing up and saying goodbye to more and more things.

Growing up means saying goodbye to more and more things.