Have you been asked to revise and resubmit your paper?
It might seem like a knock back to have your paper returned with comments to review and resubmit, but it is important to celebrate at this stage! A response such as this can be helpful and result in a much better paper - see it as a positive outcome and genuine opportunity to improve the work. Make the amendments suggested, unless it is impossible to do or you believe there is a mistake on the reviewer's part.
Challenge reviewer comments where necessary, you can even contact the editor if there is a substantive error in the review - but be mindful of the way you do so. You may encounter this reviewer again, or even review one of their papers in the future. Own up if the changes are impossible and be tactful with your challenges.
You may well have to return to the paper and rewrite it, if so, seek out support from colleagues to proof-read before you resubmit.
