We who are in Christ Jesus are secure in Him because our loving, reliable, constant, gracious Savior and Lord is in control of all things.  And He does all things well!

So when He tells us,
“…In the world you will have tribulation; but be of good cheer I have overcome the world.”  
John 16:33

We who are trusting in Him, are to do just that, ‘be of good cheer’!
The Amplified Bible says,
“…be of good cheer [take courage, be confident, certain undaunted]!…”

Cheerfulness is a balm for all who take the word of Jesus to heart.  Look at what Scripture has to say about a heart that is joyful and one that is not:
“A merry heart makes a cheerful countenance (face),
But by sorrow of the heart the spirit is broken.”  Proverbs 15:13

“A merry heart does good, like medicine,
But a broken spirit dries the bones.”  Proverbs 17:22

Proverbs 15:15 states the negative first;
“All the days of the afflicted are evil,
But he who is of a merry heart has a continual feast.”

The Amplified tells us,
“All the days of the desponding and the afflicted are made evil [by anxious thoughts and forebodings]…Proverbs 15:15a
We can see here why Scripture tells us to ‘be anxious for nothing’ (Philippians 4:6) and to ‘rejoice always’(1 Thessalonians 5:16).
The result then is,
“…he who has a glad heart has a continual feast [regardless of the circumstances].  15:15b

“Anxiety in the heart of man weighs it down,
But a good word makes him glad.”  Proverbs 12:25

Anxiety is not for those who believe for we have been given,
“…beauty for ashes, the oil of joy for mourning, the garment of praise for the spirit of heaviness…”  Isaiah 61:3
And,
“Cast your burden on the LORD [releasing the weight of it] and He will sustain you; He will never allow the [consistently] righteous to be moved (made to slip, fall or fail).  Psalm 55:22  The Amplified Bible

And again,
“Casting the whole of your care [all your anxieties, all your worries, all your concerns, once and for all] on Him, for He cares for you affectionately and cares about you watchfully.”  1 Peter 5:7  The Amplified Bible

So with great joy we heartily hold on to the promise of Philippians 4:6-7
“Be anxious for nothing, but in everything by prayer and supplication with thanksgiving let your requests be made known to God.  And the peace of God that passes all comprehension, shall guard your hearts and your minds in Christ Jesus.”  

All praise and thanks to you, Lord God Almighty     Amen