Careful with that assumption. I can see it completely backfiring. Doing the thing repeatedly can end up increasing the anxiety. If this route is taken, then "the thing" must be introduced very gradually and from a place of security.
As an example, for an arachnophobe, it would starting with something like "draw a dot. Draw a line coming out of the dot. Keep drawing lines up until 8. Pay attention to your anxiety levels and remind yourself that this is not a real spider, only a drawing. You are in control, you are safe". Then progressing to pictures of cartoon spiders, then the first picture of the most cute realistic spider that one can find, and so forth. It would be a process that takes months and it's not guaranteed to work. For example, a realistic depiction of a spider might be too much to handle even with a gradual approach.
On the other hand, if you tell that person "Close your eyes and open your hand. There, I put a tarantula in your hand, you see, it's innocuous!" that person is going to be scared of spiders for life.
I'm exaggerating, but hopefully it sends the point across.