New Bible Commentary ( p. 504) provides some background:  'The word temple in the title should be 'house'.  This could be a reference to David's house(2 Samuel 5: 11), the house of the Lord (2 Samuel 7:5; 1Kings 6: 1) or to the use of the paslm at the temple-rededication after its desecration by Antiochus Epiphanes in 165 BC.  At the time of David's own house, his sense of security would have been enormous: Zion was captured and fortified, power was increasing, possibly also the Philistines were defeated while the house was still in building.  If, in this pride-inducing period, the Lord in grace humbled David by a sickness which dashed the cup from his hand before he had time to drink it, the terms of this psalm are most perfectly suited and David learned that, as grace had brought him safe thus far, only grace can lead him home.  It was when he felt secure that he needed to cry out for mercy.'

V 1.
I will exalt you, O Lord;
for you lifted me out of the depths
and did not let my enemies gloat over me.

David still had enemies who would have been gloating over his illness and wishing him dead.  He gave God the credit for healing him.

God is able to lift us out of the depths of illness, depression, despair. Often that's when we don't feel like talking to him, but that's when he is standing by us ready and wanting to help.  that's when we need most to remember his goodness and greatness and worship him.

V 2, 3.
O Lord my God, I called to you for help
and you healed me.
O Lord, you brought me up from the grave,
You spared me from going down into the pit.

David knew he could call to God for help.  He had done it many times and knew God would answer as he had always done before.  The more we get used to calling on God, the more our faith in him grows, so it becomes easier to call on him.

V 4.
Sing to the Lord, you saints of his;
praise his holy name.

New Bible Commentary, p. 504. Saints = 'the Lord's beloved who love him back'
Quest Study Bible dictionary, p. 1748: Saints = Those dedicated to God and set apart for his service (Philippians 1:1).  All who believe in Jesus, regardless of their character or spiritual maturity.

This is a command for everyone who loves God to sing to him and praise his name - at any time, not just at worship services in the church.   David knew the value of praising God continually.

The Message: 'Sing your hearts out to God!'

V 5.
For his anger lasts only a moment,
but his favour lasts a lifetime;
weeping may remain for a night,
but rejoicing comes in the morning.

The Message:
He gets angry once in a while, but across
a lifetime there is only love.
The nights of crying your eyes out
give way to days of laughter.

Why do we sing praises to God? Among other things, becuase of God's loving nature which means that, while he does get angry about such matters as injustice and our disobedience and hurts when we ignore him, he always loves us anyway.  When we realise this, we can only feel joy, even in times of trouble and sadness.

V 6, 7.
When I felt secure, I said,
"I will never be shaken."
O Lord, when you favoured me,
you made my mountain stand firm;
but when you hid your face
I was dismayed.

The Message:
When things were going great
I crowed, "I've got it made.
I'm God's favourite
He made me king of the mountain."
Then you looked the other way
and I fell to pieces.

Like David, when things go well for us, we tend to think it's all our own doing and we get over confident and complacent.  That's when we're likely to fall over our own feet and 'come a cropper'.

And also like Peter, when he walked on the water (Matthew 14: 28 - 32). He was OK while he kept his eyes and thoughts on Jesus, but began to sink as soon as he began to take notice of the situation he was in - the water, the stormy weather - and began to be afraid.

It's so important that we remember, when we achieve success at something, that without God, it wouldn't have happened.  He is the one who has given us our skills, ability and ideas which contribute to our success.  We must give him the credit and the thanks.

V 8.
To you, O Lord, I called;
to the Lord I cried for mercy;

Quest Study Bible dictionary, p. 1746: Mercy = Compassion or kindness shown to someone instead of severity, especially to someone who doesn't deserve it.

David knew who he needed to call on.  He also knew his own shortcomings and knew he did not deserve God's help.  But he knew that God would help him anyway.  God is merciful and generous.  He wants what is best for us and will respond in our best interests when we call on him.  NB.  His response may not necessaritly be what we think we need or exactly what we've asked for.  We must trust that he knows best.

Vs 9, 10.
"What gain is there in my destruction,
in my going down into the pit?
Will the dust praise you?
Will it proclaim your faithfulness?
Hear, O Lord, and be merciful to me;
O Lord, be my help"

The Message:
I called out to you, God;
I laid my case before you:
"Can you sell me for profit when I'm dead?
auction me off at a cemetery yard sale?
When I'm 'dust to dust' my songs
and stories of you won't sell.
So listen! and be kind!
Help me out of this!"

This sounds as if David is bargaining with God.  But it's David being honest in his prayer.  This is just how he feels when he's ill, in trouble and depressed.  He feels as if God doesn't care about him.  But he knows that his feeling is false because God has been faithful to him in the past.  He trusts what he knows about God, not how he's feeling and comes to God for help.  David is not ashamed to plead with God.

Vs 11, 12
You turned my wailing into dancing;
you removed my sackcloth and clothed me with joy,
that my heart may sing to you and not be silent.
O Lord my God, I will give you thanks for ever.

David's trust in God was not misplaced.  God came to his aid, just as he had asked.  So David's wailing (or whingeing!) was turned into rejoicing.  David's unique style of praise was to dance as well as sing.
David is now full of joy and praise for God, which he vows he will do forever.

David's psalm was a wonderful witness to the grace and mercy of God.  We may not be as able to express ourselves with such poetry, but we can tell others what God has done for us.  And we can be joyful in our worship - put our praise into action.