Whilst it is true that some people ARE too heavenly minded to be any earthly use, it is also true that if Christians lose their heavenly perspective, they also cease to be any earthly use. The fact that we will live forever with God in a new heaven and a new earth gives us a radically different context in which to live. Some things that are massively important without that perspective, most obviously our own suffering, become far less negative per se. Similarly things that can otherwise get overlooked, specifically the need to share the good news of Jesus with as many people as possible, becomes far more significant. Which is NOT an excuse for trying to frighten non-Christians with stories of Hell; it's noticeable that Jesus, who is the source of our information about Hell, doesn't teach about it to those outside the faith.