Whenever you travel to another country, you need the right documentation to be admitted across their borders. I made the mistake one time of getting all the way to the Los Angeles International Airport to travel to Singapore, and I forgot to pack my passport. I heard the words "Can I have your passport, please?" and my heart just sank because I knew I didn't have it.
The eternal journey to heaven is far more serious than a trip overseas, and you have to make sure that you have the right documentation, so to speak: the finished work of Jesus Christ on the cross. But how do we live on earth responsibly while moving toward heaven eventually? How do we strike a balance between being citizens of the earth and citizens of heaven? This is something the apostle Paul modeled for us in Philippians 1.
When Paul wrote Philippians, he was in prison facing a trial, and he didn't know if he was going to live or die. In Philippians 1:19-26 especially we see him doing mental gymnastics: "I don't know which would be better: to go to heaven or to stay on earth." In verses 23-24, he wrote that he was "hard-pressed between the two, having a desire to depart and be with Christ, which is far better. Nevertheless to remain in the flesh is more needful for you." He was caught between a rock and a hard place.
Deep in his heart, Paul wanted to depart this life. The language he used describes the breaking up of a camp to move on to a permanent location. And for Paul, it was all about that permanent destination: to be with Christ. This is what makes the death of a believer so sweet. Anything we've encountered of Jesus in this life is going to pale in comparison to actually being in His presence and seeing His face, and Paul knew that.
Even so, Paul was willing to persist here on earth: "Nevertheless to remain in the flesh is more needful for you" (v. 24). Even in prison, he was thinking of how other people could benefit from his ministry, and he was determined to be fruitful.
This is how Paul summed up his whole approach to life, to being a citizen of heaven on earth: "For to me, to live is Christ, and to die is gain" (v. 21). Only someone who says, "To live is Christ" can say, "To die is gain." Just try to recast that sentence according to whatever your life motto happens to be. "To live is money, and to die is to leave it all behind," right? You can't take it with you. Or "To live is notoriety, and to die is to be forgotten." But if you can say, "For me to live is Jesus Christ," then you can say, "To die is gain."
You need to be ready to die, but you also need to be ready to live until you die. We all live in between two worlds, so keep the eternal in mind as you move through the temporal. That was Paul's way of living, and it can be yours, too.