I think the logic goes something like this: If we don't expect greatness, if we don't expect to find love and be healthy and successful, well we're not going to be disappointed when these things don't happen.
彼らの論理はこんな感じです 多くを期待しなければ 愛と健康と成功が 手に入ると期待しなければ 手に入らなかった時に 落胆せずに済みます