The intention behind the reprimand is to help the other person realize what has gone wrong and he must feel motivated for future good performance, in addition that he develops more regard for you for helping him develop.
To begin with it is a must to make sure that he is clear regarding the goal both of you have agreed upon. Tell him that you will give your feedback on the performance. Once the performance is complete, then directly ask him what happened. Maintain eye to eye contact.
If the performance is matching the direction of the goal it is right otherwise wrong or simply unacceptable. In that case he is feeling caught red handed. At that moment convey true negative feelings – how bad you are feeling because of that performance. Discuss the negative performance only and not the person at all. Maintain an uncomfortable silence so that he feels the echo of your negative feelings within the depth of his mind. Now he is feeling cornered without any hope to escape.
It is your responsibility to bring him out of the negative feelings. It is always wise to leave the person on a positive note. Give a supporting touch and praise the person. But how can you praise someone when something wrong has happened. Praise for something good that has been done by him in a similar past performance. Firmly tell him not to repeat this kind of negative performance in the future. This way the person is realising one’s wrong doing, is immediately feeling motivated for future good performance and feels more regards for you for helping him develop.