When God speaks, He’s not really speaking to that situation; nor to anyone or anything. God’s words are primarily for His Spirit.
In creation, for instance, the Holy Spirit was already present in the midst of all the formlessness, emptiness and darkness.
He was there waiting for the Word to come forth.
Genesis 1:1-3 NIV
 In the beginning God created the heavens and the earth.  Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters.  And God said, “Let there be light,” and there was light.
You see, when God said, “Let there be light,” He was giving a command to His Spirit. He wasn’t speaking to the darkness. He wasn’t speaking to the formlessness, emptiness, and darkness of the earth. He wasn’t even speaking to light.
He was speaking to His Spirit. Letting Him know what to produce.
And as soon as God made His desire known, the Spirit produced it: “And there was light.”
We see this same mystery at work in Jesus’s earthly ministry.
Luke 5:17 KJV
 And it came to pass on a certain day, as he was teaching, that there were Pharisees and doctors of the law sitting by, which were come out of every town of Galilee, and Judaea, and Jerusalem: and the power of the Lord was present to heal them.
The power of God —Who else but the Holy Spirit Himself—was present to heal the sick. Such that whenever Jesus gave the Word, the Holy Spirit bore the fruits!
See this at work in the following story.
John 5:1-9 NIV
 One who was there had been an invalid for thirty-eight years.  Then Jesus said to him, “Get up! Pick up your mat and walk.”  At once the man was cured; he picked up his mat and walked. The day on which this took place was a Sabbath,
Jesus said to him, “Get up! Pick up your mat and walk.”
Certainly, the invalid was in no position to execute such word. Yet, he did.
But before he did, something happened to him: He was cured. How did that happen? Who cured him?
You see, the moment Jesus gave that word, the Holy Spirit executed it. The crippled man didn’t obey that word. The power of God, the Holy Spirit, executed it in the man’s life and produced the miracle.
Again, observe this mystery at work in the destiny of the Virgin Mary. She was told she would give birth to the Messiah of the world.
She wanted to know what to do: “How in the world could this be? I don’t have what it takes. What should I do? What is required of me?”
And I can imagine the angel thinking, “Don’t be ridiculous! Nobody is expecting you to do anything. This is all the work of the Holy Spirit!”
Luke 1:34-35 NIV
 “How will this be,” Mary asked the angel, “since I am a virgin?”  The angel answered, “The Holy Spirit will come on you, and the power of the Most High will overshadow you. So the holy one to be born will be called the Son of God.
In other words, the angel told Mary, “Absolutely nothing! You don’t have to do anything. The Holy Spirit will take over your body and produce His fruit.”
Nevertheless, much to her credit too, she had the right response. One that I believe is the perfect response for people of faith.
Luke 1:34-38 NIV
 “I am the Lord’s servant,” Mary answered. “May your word to me be fulfilled.” Then the angel left her.
All she did was receive that word in her heart.
Now, the point in all this is that when God sends His Word, it’s really not for you to try to use your pathetic fleshly abilities to attempt to execute His Word. That’s arrogant and presumptuous. Because you will ultimately collapse in the attempt.
And, let’s even say you succeed in your attempt, you’ll merely produce works of the flesh—filthy rags.
Instead, learn this: Whenever God gives a command or instruction, He’s not necessarily telling you what to do.
He is rather showing you what His Spirit is producing in your life. He is revealing to you what His Spirit is doing in the invisible realms of your destiny.
Reflect on this two scriptures. Take careful not of my emphasis:
Ephesians 3:20 NIV
 Now to him who is able to do immeasurably more than all we ask or imagine, according to his power that is at work within us,
Philippians 2:13 NIV
 for it is God who works in you to will and to act in order to fulfill his good purpose.
And all you need to do is receive that word like Mary.
Be it unto me according to your word.
Holy Spirit, help me to surrender to you.
Take your place and have your way in my life.
So, instead of trying to obey God, laboring in vain and being wearied, get on your knees. Then ask the Holy Spirit to bear His fruits in your life.