"Humble yourselves therefore under the mighty hand of God, that He may exalt you in due time. Casting all your care upon Him; for He careth for you." 1 Peter 5:6-7
I've learned that as each day passes, I need God more and more. Even though I have become more self-supporting, more educated, more theologically sound, more responsible, more loving, more caring, more hospitable, and on an on, I recognize that all of my proficiencies still require a great deal of improvement. God wants me to cast my cares upon Him. Why wouldn't I. God can handle my problems, whether self-inflicted or brought on by others or from natural causes, better than I.
God says "cast all your care upon Him." All is more than just the big picture things that you might currently be giving over to God. God knows that between your wisdom and His, you are better off with His. God knows that if you do cast all your cares upon Him, that He can handle them and do mighty exploits on your behalf. It's not that God looks at us as unable or that nothing that we do is good enough. That's not the case. God wants you to cast our cares upon Him so that you can co-create with Him the events of your life. God cannot live your life for you and living your life without a constant, meaningful and measurable relationship with God leaves you powerless against certain obstacles.
The problem with holding back in giving all your cares to Him is that you start to build a belief system where you are the deciding factor as to how much of your life God gets to be involved in. You can create for yourself a religious system with formulas that are not from God. You have to give it all to God or you run the risk of not following God when you think you are following God.
I think casting all your cares upon God is good advice.