Why does the Gene feel better when he thinks Finny has been sabotaging his efforts to be head of the class

Gene, an academic perfectionist, laments his poor performance on the test to Finny; Finny mocks Gene's ambition to be first in their class, and Gene begins to believe that Finny doesn't want him to do well in school, so that he will come out ahead. Finny excels in athletics, and is definitely the best in the school; Gene knows that he can be the best in the school in academics, but thinks that Finny's high-jinks and his attempts to take up Gene's time are Finny's attempts to make sure that he comes out ahead in the relationship. Gene's jealousy, whether merited or not, begins to take him over; he decides that he cannot trust his "friend," and Finny's statement, that had been so touching the previous evening, of Gene being his best friend, Gene now believes to be false.

Gene soon skips his merrimaking with Finny in favor of studying very hard; he begins to overtake Chet Douglas, Gene's only academic equal, and is proud that he is doing so well in his war against Finny. Finny also begins to study more, but Gene says that Finny is weak academically because he is unable to relate to the kinds of tests they have to take. But Gene finds it hard to keep on hating Finny, because everything is so beautiful and relaxed that summer; he has to make himself feel resentment, which proves to be very hard to do.