Paul writes something fascinating in Phil 3.14:
κατὰ σκοπὸν διώκω εἰς τὸ βραβεῖον τῆς ἄνω κλήσεως τοῦ θεοῦ ἐν Χριστῷ Ἰησοῦ.
I run forth towards the goal, towards the prize of the upwardly call of God in Christ Jesus.
One of the first things to note about this passage is the verb Paul uses. He is using an athletic metaphor: like a sprinter seeking to be the first across the finish line, Paul is running towards a goal, towards a definite end. The significance of the athletic metaphor should not be overlooked. To speak of the Christian life as a race towards a goal, an athletic endeavor, is to give it a certain nature and essence. The Christian life is not only rest and relaxation and a break from all you worries; it also demands real exertion, real effort, real discipline, real training. Paul writes to Timothy: Train yourself in godliness (1 Tim 4.7).
Part of Paul's maturity (cf. Phil 3.15) lies in the realization that he has not yet obtained the prize or been perfected (v. 12). He realizes that there is still work to be done, still a race to be run. He doesn't think he's got it all, or that he's finished with all his work. More than that, he tells us that the mature among us ought to think in this way as well (v. 15).
Now what is the prize towards which he runs? He is talking about the prize of the "upwardly call of God." Certainly he is talking at least about resurrection, since that is what he mentions in vv. 10-1. But there is something to be understood by the interesting adverb he uses. He uses an adverb to describe a noun: τῆς ἄνω κλήσεως τοῦ θεοῦ, the upwardly call of God. What does this mean?
I take this as a reference to theosis. The call of God is to bring a person up, up to heaven, where God is. This is not gnostic escapism from earth; I am talking about the deification of the earthly creature Man, not the escape from the material realm. The upward motion is not spatial but metaphysical; it is ascending the ontological ladder up to God. It is a bringing-down of God to Man, and yet it is simultaneously a lifting-up of Man to God; God's descent is the ascent of Man. The call of God in Christ Jesus, then, is to go up, ever up, to the level of Christ Jesus, who represents perfected humanity.
But for this end there is work to be done. There is a race to be run, labors to be had, efforts to be exerted. So fight on! Keep on running! Keep up the race!