Only let your conduct be worthy of the gospel of Christ, so that whether I come and see you or am absent, I may hear of your affairs, that you stand fast in one spirit, with one mind striving together for the faith of the gospel… (Philippians 1:27, NKJV)
Paul said the Philippians were to be single-minded in striving for the gospel. Sadly, on earth, we are often distracted from spiritual striving and focus on physical striving. Many strive endlessly for that mansion, that lofty position, that perfect body, and that life filled with pleasure, when Jesus promises that one day He will build us in heaven a mansion on streets of gold, give us a position reigning with Him, grant us a new and perfect body that will never decay, and place us in an environment of unspeakable pleasure and delight. Some who have strived all their lives to earn such things will one day see them handed over by Jesus as a gift unrelated to any such striving. Why strive for the fringe benefits of heaven coming to each true believer automatically? As long as you are going to strive anyway, why not strive for the faith of the gospel?