You have probably heard this: "Every morning in Africa, a gazelle wakes up. It knows it must run faster than the fastest lion or it will be killed. Every morning a lion wakes up. It knows it must outrun the slowest gazelle or it will starve to death."
It doesn't matter if you are a lion or a gazelle. When the sun comes up, you better be running.
"LORD" as used here in Hebrew means - Eternal, Jehovah, self-existent. The One with no beginning and no end. "I am the Alpha and the Omega," says the Lord God, "Who is, and Who was, and Who is to come, the Almighty." Rev. 1:8; 21:6; 22:13.
Piece all these truths together and you get: "Throw and hurl everything that has been given to you onto the Lord. Everything that has been given to you, you are to throw onto the Lord and not to take it back."
"Sustain" in Hebrew means: "To keep in and contain, To abide, remain with and reside, To receive, comprehend and guide, To feed, nourish, make provision for and provide sustenance for."
God makes this personal - "You" - means God is willing and able to do this for you, just the way you are. No changes are needed to come before the Lord God Almighty.
Add it up like this: The Lord God Almighty will never ever cause the just, clean and righteous person to slip and fall or be carried, cast, or be out of course and be fallen in decay. The Lord God will keep His child, that means the one who trust in Him and loves Him and obeys Him in Spirit and in Truth, He will keep that child cared for and nurtured, steadfast in His Love and protection.