Instruct: Classify a given Amazon review into positive or negative sentiment.
Query: Best investment, restored sanity!

I hated to have to resort to this method, but I was about to give up on this dog due to its incessant barking. We rescued her several years ago, and love everything about her, except the constant high pitched barking. Nothing else worked, and at times, I thought I was losing my mind and vowed to get rid of her. I read all of the reviews on Amazon about this product and decided to give it a try. It only took a few times wearing the collar, and she learned not to bark. Now she quietly whines to go out or be let in, and if a week or more goes by and she starts to bark again, I put it on for a few minutes, and she quickly re-learns. I actually am falling in love with this dog, rather than just tolerating her. If you are in the same boat, try this collar!