"Therefore we do not lose heart, but though our outer man is decaying, yet our inner man is being renewed day by day. For momentary, light affliction is producing for us an eternal weight of glory far beyond all comparison, while we look not at the things which are seen, but at the things which are not seen; for the things which are seen are temporal, but the things which are not seen are eternal." ~ 2 CORINTHIANS 4:16-18
In the text above, I've underlined a few verbs, or action words that Paul uses. We should note that they are all in the present tense, denoting current, continuous action. Paul is not speaking of something that has already gone by, or once done and finished, but a process that is perpetually ongoing. There may sometimes be a certain amount of earthly satisfaction to have performed a deed or action and moved on, getting it "off our list", as we say. But I believe we should recognize the greater sense of spiritual fulfillment in knowing that Christian living is an ongoing process that we engage in continually, and that brings into our lives blessings that are new every morning... (Lamentations 3:23).
The text under consideration (2 Cor.4:16-18), challenges our focus, commending us to look not at the things that are seen, but at the things which are not seen... Used in this way, the dictionary defines focus as a center of activity, attraction, or attention. Thus the center of our attention should be those unseen things. In fact, the Greek word from which look is translated in vs.18 is a term which means to take aim at, as in watching from a distance. So, our focus should be fixed on, our aim should be directed toward, not the things that are seen but the things that are not seen.
I know what you are thinking, "How can we aim at something that we can't see?" The instruction is not directing us toward something that is hidden or invisible, but that which is of the future, that which is yet to come. But lest we misunderstand, and take the disposition of the one who is always chasing the elusive fortune just around every corner, read again the definition of these unseen things contained in verse 18: for the things which are seen are temporal, but the things which are not seen are eternal. The clear contrast here is earthly things versus heavenly things; physical versus spiritual. This is in perfect keeping with the Lord's instruction in Matthew 6:19-21, "Do not store up for yourselves treasures on earth, where moth and rust destroy, and where thieves break in and steal. But store up for yourselves treasures in heaven, where neither moth nor rust destroys, and where thieves do not break in or steal; for where your treasure is, there your heart will be also."
There is no better commentary on the need to focus on the heavenly than the one Holy Spirit provides for us in Hebrews 11. The chapter opens with verse 1's definition of the faith we must have as the conviction of things not seen. Then over and over, He gives us illustrations of that faith from the lives of Old Testament notables.
In verse 7, in view of things not yet seen, Noah obeyed, building the ark. Verse 8 tells of Abraham's willingness to undertake a journey without even any knowledge of where he was going, because of his great faith. In verse 10, he exhibited that forward-looking faith by looking for the city which has foundations, whose architect and builder is God. Verse 13 says that all of those faithful servants perished without receiving the promises, but having seen them and having welcomed them from a distance... They were focused on a better country, that is, a heavenly one (vs.16). Verse 26 explains that Moses knew to choose serving God over Egypt because he was looking to the reward.
With more space, we could talk about the need for fixing our eyes on Jesus, the author and perfecter of faith (Heb.12:2). But surely we can see that all this reminds us that for the faithful child of God, the best is yet to come if we'll stay focused on the eternal!