"You shall eat the fruit of the labor of your hands; you shall be blessed, and it shall be well with you." -Psalm 128:2
Our spreading God's word depends greatly on our reputation. Would you be more willing to listen to a happy, upbeat person about their life, or someone who walks around constantly gloomy and sad and depressed and hates everyone and everything? I mean, I don't know about you, but I don't really want to follow the lifestyle of someone who hates their life and everyone and everything in it. It doesn't exactly appeal to me. However, if you're always positive about your work, your school, your life, people are going to be more willing to listen to you. And not only are people going to want to listen to you if you love your life, aren't they going to appreciate God's people more if they're always over-achievers? Won't it give God's people a better reputation if we are always working hard and looking nice and doing a nice job? People don't really look up to people who are always slacking off. As God's people we are to be examples of His word, even in something seemingly irrelevant.
I know it seems like it wouldn't matter, but not only is it going to improve your grades or pay check, but people are going to get a better opinion of Christians. The world seems to believe that Christians are just lazy bums who think they're better than everyone else. This is not the case though, but how can we prove that if we are lazy bums who think we're better than everyone else? We need to show others that we're human, and that we are Christians, and that we are good. When people start noticing these things about Christians, they're going to start noticing them about God.
I know it seems silly and ridiculous that something as simple as going the extra mile in whatever you're doing can help further God's kingdom, but believe me, it can. You may not see the results, but they'll be there. I'm not saying that if someone sees you working hard they'll automatically convert to Christianity, but it's a lot easier to listen to someone you respect than someone who doesn't seem to deserve any respect what-so-ever.