You're in God's hands, but in a way He's also in yours, He's at your command like the genie of Aladdin's Lamp! You can command the Lord? Yes, if you're in His Spirit and in His Will, desiring only those things which glorify and please Him, and delighting yourself only in Him, you can command whatever you want. (Psa.37:4) If you're righteous, doing the right thing and trying to please God, love Him, and have faith in His Word, He's promised to answer your prayer!
So much of what God does depends on your will and your action and what you want and how you pray! He has confined Himself and His operations to your faith and your requests. "Ye have not because ye ask not." (Jam.4:2) He's just waiting on you to command the situation.
Can you change God's mind? Within certain limits, yes. God's overall plan has never changed, His overall will has never changed. But in certain details you can change His mind, otherwise there would never be any point in praying. If prayer doesn't change things, why pray?
Prayer moves the hand and heart of God! He enjoys using us, confining the majesty and the power of His omnipotence to the hands of frail men and women! So pray!