What are you thinking about?
Here are some questions to ask about it:
Is it TRUE?
unconcealed, true, true in fact, worthy of credit, truthfulIs it HONORABLE?
venerable, honorable, grave, serious, dignifiedIs it JUST?
right; righteous; especially, right in the eyes of GodIs it PURE?
chaste; in a condition prepared for worshipIs it LOVELY?
pleasing, acceptable, gratefulIs it COMMENDABLE?
well reported of, spoken in a kindly spirit, laudable, reputableIs it EXCELLENT?
good, a gracious act, virtuous, uprightIs it WORTHY OF PRAISE?
commendable, approved of by God
If YES - then keep on thinking about it. Dwell on these good thoughts and be at peace.
If NO - then do not dwell on these thoughts. They will only bring discontent.
NOTE: The definitions for the words above came from the Text Analysis of Philippians 4:8, found on BIBLE HUB.