Americans spend billions of dollars each year on psychotherapy. Sometimes this is money well spent. I myself, for example, benefited from seeing a Christian counselor when I suffered depression several years ago. Sometimes, however, psychotherapy is not such a good investment. I know people who were offered bad advice by incompetent practitioners and came out of the process worse and poorer. The Book of Proverbs is a great psychotherapist, and the best part about it is that its advice is free.
Let’s take a look at what it says about matters of the heart.
An anxious heart weighs a man down,
but a kind word cheers him up (12:25).
Hope deferred makes the heart sick,
but a longing fulfilled is a tree of life (13:12).
A heart at peace gives life to the body,
but envy rots the bones (14:30).
A happy heart makes the face cheerful,
but heartache crushes the spirit (15:13).
A cheerful heart is good medicine,
but a crushed spirit dries up the bones (17:22)
At one level, what these proverbs teach is both obvious and trite. Positive emotions have positive effects on us, but negative emotions have negative effects. But these proverbs are not merely describing the relationship; they are prescribing certain actions. Speak kindly to an anxious man! Don’t defer hope indefinitely! Don’t envy others! We want to be happy, but happiness is the emotional byproduct of moral living. Do the right thing, and you’ll be happy.
Part of doing the right thing is speaking kindly to others.
The tongue that brings healing is a tree of life,
but a deceitful tongue crushes the spirit (15:4).
A cheerful look brings joy to the heart,
and good news gives health to the bones (15:30).
Our words have an incredible power to cheer others up. Unfortunately, some souls are so sour that not even singing songs is successful therapy.
Like one who takes away a garment on a cold day,
or like vinegar poured on soda,
is one who sings songs to a heavy heart (25:20).
This last proverb reminds us that we can be only so helpful to others. At some point, they are morally responsible for their emotional states.
Each heart knows its own bitterness,
and no one else can share its joy (14:10).
As water reflects a face,
so a man’s heart reflects the man (27:9).
Indeed, in some circumstances, it’s not even our job to try to cheer people up.
A man tormented by the guilt of murder
will be a fugitive till death;
let no one support him (28:17).
They are depressed because of immorality. Until they confess and make restitution, their guilt and shame will continue to sadden them.
In fact, while we all want to be happy, some level of sadness is simply part of the human condition.
Even in laughter the heart may ache,
and joy may end in grief (14:13).
We live in a sinful world, so some level of sadness is just our lot in life. But so is some level of happiness if listen to Dr. Proverbs wise counsel.
GeorgePWood.com 
I once heard Jan Dravecky give a talk about overcoming depression. As I recall, she mentioned Proverbs 25:20 (“one who sings songs to a heavy heart”) in the context of other Christians who told her that she would be fine and expected her to be cheerful and happy although she was clinically depressed. I thought that the verse is telling us to be sympathetic to people who are in pain, grieve with those who grieve, etc.