If you feel down in the dumps, or your thoughts are just ruminating I suggest trying Bloom app on iPhone. It uses cognitive behavioral therapy CBT for self-guided video lessons. CBT is scientifically proved to work, but moreso, has scriptural evidence as well to support it.

"As he thinks in his heart, so is he." (Proverbs 23:7)

and Jesus said:

Matthew 16“Don’t you understand yet?” Jesus asked. 17“Anything you eat passes through the stomach and then goes into the sewer. 18But the words you speak come from the heart—that’s what defiles you. 19For from the heart come evil thoughts, murder, adultery, all sexual immorality, theft, lying, and slander. 20These are what defile you. Eating with unwashed hands will never defile you.”

Thoughts -> Feelings -> Action -> Character