What causes heartfelt disappointment?

What causes heartfelt disappointment,
Emptiness and discontentment?
Is it not a faithless living,
Not trusting in what God is giving?
Can you conceive you know better,
Are you not locked in a fetter,
Of circumstances you cannot control,
In the sins of your own soul!
The One who made all we see,
Controls each element endlessly,
Never tiring or letting loose,
The laws of His universe.
If He be thus involved,
Are not all your problems solved?
For if He sees the little bird,
Think you not your voice is heard.
So be joyful, trust His grace,
Let obedience fill the space,
Where discontent and sorrow once abode.
Let them know longer incommode.
The only sorrow to feel now,
The only sorrow to allow
Is that for your sin,
And those of your fellow men.
Surrender to the God above,
Who sent down to us His love.
Planned our days, determined our end,
Calling out His ones to befriend.
So think not on what He has not given,
Rather be glad your among the living.
Enjoying His smiles instead of His wrath,
Thankful for all He's done on your behalf.
For what you thought was so much less,
Turned out better than your supposed best.