Have you ever "trained" or "reprogrammed" yourself to stop saying or doing a certain thing that you habitually do/say?

What seems like eons ago, I had a boss who always said “not for nothing”. I remember hating the phrase then, but because I worked in such close contact with her and eventually became friends, I picked it up and now I find myself saying it more than I’d like.

Also, I am told I do this eye flutter thing that makes me look like a total bitch, and I don’t even realize I’m doing it.

How does one break themselves of these types of bad habits when one doesn’t even realize they’re happening until they’ve already happened?