Dwell on these things

Finally, brethren,
whatever is true,
whatever is honorable,
whatever is right,
whatever is pure,
whatever is lovely,
whatever is of good repute,
if there is any excellence and
if anything worthy of praise,
dwell on these things.
Philippians 4:8 NASB

I like Eugene Peterson's Message Bible paraphrase, too:

Summing it all up, friends, I'd say you'll do best by filling your minds and meditating on things true, noble, reputable, authentic, compelling, gracious—the best, not the worst; the beautiful, not the ugly; things to praise, not things to curse.

That entire Philippians 4 chapter is rich enough for someone to mine for a lifetime.

C. S. Lewis in "The Last Battle" has Lord Digory say about the new Narnia “Its inside is bigger than its outside." “Yes,” said Queen Lucy. “In our world too, a Stable once had something inside it that was bigger than our whole world.”

It is fascinating to me that Paul wrote the letter to the church at Philippi while imprisoned in Rome (" ... I am in chains for Christ." 1:13 NIV) .

Somehow being imprisoned doesn't seem exactly conducive to thinking on good things.