What type of figure of speech is "let's not let our imaginations run away with us," and why?

I would tell my supervisor that terry has had many near misses and is not experienced

It is an example of personification. Personification is when a nonhuman, or an inanimate object, exhibits natural human actions or traits. In this case, imaginations are the inanimate object, which is being portrayed to be running away with us, the human trait is running.