From BibleGateway (English Standard Version):

2 Corinthians 4:16-18

So we do not lose heart. Though our outer self is wasting away, our inner self is being renewed day by day. For this light momentary affliction is preparing for us an eternal weight of glory beyond all comparison, as we look not to the things that are seen but to the things that are unseen. For the things that are seen are transient, but the things that are unseen are eternal.

Hebrews 12:3-11

Do Not Grow Weary

 Consider him who endured from sinners such hostility against himself, so that you may not grow weary or fainthearted. In your struggle against sin you have not yet resisted to the point of shedding your blood. And have you forgotten the exhortation that addresses you as sons?

  "My son, do not regard lightly the discipline of the Lord,
   nor be weary when reproved by him.
For the Lord disciplines the one he loves,
   and chastises every son whom he receives."

It is for discipline that you have to endure. God is treating you as sons. For what son is there whom his father does not discipline? If you are left without discipline, in which all have participated, then you are illegitimate children and not sons. Besides this, we have had earthly fathers who disciplined us and we respected them. Shall we not much more be subject to the Father of spirits and live? For they disciplined us for a short time as it seemed best to them, but he disciplines us for our good, that we may share his holiness.  For the moment all discipline seems painful rather than pleasant, but later it yields the peaceful fruit of righteousness to those who have been trained by it.