Because: ① Treat friends with principles, be firm in the face of principles, and cannot maintain the so-called friendship at the expense of principles. To develop sincere friendship, we should learn to be tolerant and generous, rather than haggle over every ounce. But tolerance is not cowardice, nor does it mean unprincipled connivance and submission to wrong behavior. In the process of making friends, we should not only adhere to principles and distinguish between right and wrong, but also tolerate and seek common ground while reserving differences. We should unify the two.