"No one can serve two masters. Either he will hate the one and love the other, or he will be devoted to the one and despise the other. You cannot serve both God and Money." Matthew 6:24
Store up for yourselves treasures in heaven.
Have good vision.
First, Jesus talks about two ways to store treasure (earth or heaven), and then two ways to see (with good eyes or bad eyes), and now He talks about two people you can serve. When He says "serve," though, it's not something that we, as westerners, can really understand easily. Jesus meant that no one can be a slave to two masters. Sure, you can work for two different employers (I've been doing that for quite a while), but if you're a slave of someone, then that person owns you...completely. Of course, we don't like to think of God a slave-owner. But the truth is, all of God's children are his bondservants.
A bondservant (doulos in Greek means "slave") is someone who loves his master so much that he is willing to give up his entirety to serve his master. That means that God is not my owner because He's all-powerful and forces me to be His subject, but rather His love for me spawns a love in me for Him that is so powerful that it compels me to serve Him. What greater joy is there than to serve the Almighty? I have found none.
May you choose to be God's slave. Today. Tomorrow. Forever.