This post explains why it's so important to think about what you're thinking about, and then turning your thoughts around if they're leading you down the track to anxiety, panic, or hopelessness.
Favorite part: "We’re completely wrong-headed whenever we lapse into thinking that
private devotions somehow wins merit points with God. Devotions aren’t
for impressing God or anybody else. They are for daily pointing us in
the right direction and fueling the engine of our trust in God."