Because God is God, He will accomplish what He wants to accomplish. He is the one who is all-powerful, all-knowing, and present everywhere. He is holy and just. He has an agenda that wins out over our own personal agendas. He has an agenda that trumps the agendas of all presidents, prime ministers, monarchs, dictators, and governments. He will accomplish His will in this world with or without our obedience. His desire, though, is a life that is yielded to Him.
And so, He allows people to enter or exit our lives. He allows tragedy to come upon us, whether it be a job loss, a financial crisis, marriage problems, or an incurable disease. We can get to the point where all we are left with is ourselves and our relationship with God. At this point, we come to the place of total dependence on Him, exactly where He wants us to be. And that's just like God, allowing overwhelming circumstances to bring us to the point of brokenness, humility, dependence, and surrender. He wants all of us, not just part of us. Henry Blackaby, the author of several books including the well-known Bible study Experiencing God, has quoted on several occasions from an unknown source, "The world has yet to see what God can do through one person totally yielded to Him."
I don't know where you're at today. Perhaps, right now, your life is blessed and worry free - congratulations. But maybe, just maybe, your locked in a struggle where there's no solution. You can't fix this one, but that's a good thing. God has placed you in a position of total reliance on Him. Walk in faith. Be in the Word. Pray for God to accomplish what He wants to accomplish in and through your life. Humble yourself and be teachable through the difficulty. Experience God through the journey.