Software development depends on cooperation between people, and the way it works can define the future of the software project. Developers emotions affect their productivity and way they work, yet there is little information abouthow developers can influence the mood of each other. As a first step toward understanding how feedback may affect the developers’ sentiment, this paper analyzes the mood variations on more than 78k pull requests and 268k pull comments on GitHub. We found that in 31.16% of the cases the developers presented a significant mood variation within one hour when receiving feedback on their pull requests. The variation reduces to 18.16% when evaluating one day before and after the commentary. In software projects with less than 34k lines of code, the number of developers that never contribute again after receiving a negative commenton the first pull request is 10.97%; this number more than doubles to 24.02% when evaluating projects with more than 197k lines of code.