The LORD is your keeper; the LORD is your shade on your right hand.  The sun shall not strike you by day, nor the moon by night. (ESV)
The LORD is your keeper Shamar / phulasso Keeps a garden / shepherds watching their flocks
The LORD doesn't just keep us. He is OUR keeper. The LORD himself is my personal keeper. He is mine and I am his. We are kept personally by the Creator of heaven and earth.
Though I walk through the valley of the shadow of death, I will fear no evil – the LORD is our keeper – at all times – day and night – we may fear no evil. He keeping us, preserving us, watching over us closely
The LORD is your shade on your right hand
Shade // right hand Journey to Jerusalem. Sun shining on left, shade on right. The LORD himself is our shade.
Everywhere we go our shadow comes with us. When the sun shines brighter, our shadow gets stronger.
Everywhere we go, the LORD is the shade on our right hand. When the heat of the sun gets hotter and more intense, the shade just grows more powerful and offers more comfort.
Don't complain about the heat of the sun – get into the shade.
Step into the shade. Step into his presence.
Psalm 91:1–2  He who dwells in the shelter of the Most High will abide in the shadow of the Almighty.  I will say to the LORD, “My refuge and my fortress, my God, in whom I trust.” (ESV)
The sun shall not strike you by day Nor the moon by night
Day and night. All the time.
The moon by night
Moon by night – The reference to the moon may simply lend poetic balance to the verse, but it is likely a reference to the primitive belief that the moon was dangerous and could have adverse effects one's mind. They believed that the rays of the moon had an abnormal effect on the eyes and could cause brain damage. We've all heard the familiar English expression “moonstruck” (mentally unbalanced, romantically sentimental, lost in fantasy) which apparently reflects this strange ancient belief. The etymology (study of the linguistic development of words) of the English word “lunatic” is from the Latin word lunaticus, which is derived from the Latin word luna reflecting the belief that lunacy fluctuated with the phases of the moon. (Merriam-Webster) Whether the psalmist meant to address such pagan beliefs is uncertain.
Epileptic = Greek = lit. moonstruck
It is the very error of the moon; She comes more near the earth than she was wont, And makes men mad.” Othello, v. 2.
We are not in danger from the moon. It is not a thing to be moonstruck in the way that it creates mental illness or epilepsy.
But we do live a really tough society. Pressure on Christianity. Increasing pressure. That can affect us and