Does seeking heavenly things make you useless on earth?
No. Colossians 3 teaches believers to seek things above and set affection on things above, but that does not mean being so heavenly minded as to be no earthly good. It means priorities are set heavenward; it is practical Christianity, not a call to a Spartan life.
Les explains from Colossians 3:1-3 that because believers are risen with Christ and identified with His death, burial, and resurrection, they are to seek things above and let those things be their priority. He clarifies that this does not mean becoming so heavenly minded that one is no earthly good. Instead, it means our priorities are set heavenward. Verse 2 says to set affection on things above, not on things on the earth, and Les calls this practical Christianity. It does not mean a person must be frugal, cannot enjoy anything, or must live Spartan.
If ye then be risen with Christ, seek those things which are above, where Christ sitteth on the right hand of God.