Definitions

All: The whole amount or quantity; As much as possible; nothing but; completely taken up with, given to, or absorbed by.

Everything: all that exists; all that relates to the subject.

From Webster's Ninth New Collegiate Dictionary

God Has Given All

What, then, shall we say in response to this? If God is for us, who can be against us?  He who did not spare his own Son, but gave him up for us all--how will he not also, along with him, graciously give us all things?    (Romans 8:31-32 NIV)

In him we have redemption through his blood, the forgiveness of sins, in accordance with the riches of God's grace that he lavished on us with all wisdom and understanding.
(Ephesians 1:7-8 NIV)

And my God will meet all your needs according to his glorious riches in Christ Jesus.    (Philippians 4:19 NIV)

"You are worthy, our Lord and God, to receive glory and honor and power, for you created all things, and by your will they were created and have their being."    (Revelation 4:11 NIV)

We Give All to Him

Blessed are they who keep his statutes and seek him with all their heart.
(Psalms 119:2 NIV)

Trust in the LORD with all your heart and lean not on your own understanding; in all your ways acknowledge him, and he will make your paths straight.    (Proverbs 3:5-6 NIV)

"Again, the kingdom of heaven is like a merchant looking for fine pearls. When he found one of great value, he went away and sold everything he had and bought it.    (Matthew 13:45-46 NIV)

Jesus replied: "'Love the Lord your God with all your heart and with all your soul and with all your mind.'   This is the first and greatest commandment.    (Matthew 22:37-38 NIV)

But whatever was to my profit I now consider loss for the sake of Christ.  What is more, I consider everything a loss compared to the surpassing greatness of knowing Christ Jesus my Lord, for whose sake I have lost all things. I consider them rubbish, that I may gain Christ and be found in him, not having a righteousness of my own that comes from the law, but that which is through faith in Christ--the righteousness that comes from God and is by faith.    (Philippians 3:7-9 NIV)

Wouldn't it be strange if God's word said to trust God with most of your heart or to love God with most (or some) of your heart? It just wouldn't work. If all or everything were left out, God would only be part of the answer. There would be something else we would need or could benefit from. If we needed God plus something else, where would that leave God? Without getting into any detailed discussion, you can see how ludicrous it would be if God where not our all and everything.
 
Our relationship with God, then, is a relationship of "all". He has given us His all to the extent that He gave completely of His own life.  From our perspective, He is so exceedingly and infinitely great and wonderful that we can and should trust Him and love Him with all our heart.What else could there possibly be in this world or in our lives which is worthy of any consideration compared to our awesome and loving God? Is your relationship with God less than you know it could be? Do you give to Him your all? We can discover the fullness of a joy filled relationship with Him only as we respond to Him with our all.
 
I could ask the question what "all" means, but we do clearly understand the concept. If we, for example, "drink all the soda" or "carry all the items", we understand that nothing remains or is left. The same concept applies in the spiritual realm. Trusting God and loving God with all our hearts simply means what it says. We don't need to compare ourselves with others, even if we judge ourselves to be better than others in our love and devotion to God. He is most worthy of our everything and our all. There is no reason to make it complicated nor is there any reason to do this gradually or in steps. God can and should be trusted with every element of our lives right now. Some might say we should give Him more and more as we learn to trust Him, but in some sense, doesn't this imply that we don't really trust Him 100% so we have to "check out" His track record ourselves and then trust Him more? Give Him everything. Don't "lean on your own understanding" or what do what others around you are doing. Give Him everything.
 
I would suggest this is the "high road" of spiritual growth. Proactively trust God with all your thoughts, all your dreams, all your hopes and all your concerns. Love Him and seek after Him with all your heart. Fill your every moment with worship and trust of Him. Anything or anyone else is less. Anything apart from Him is less. Delight in Him in all things. Why spend a single moment apart from Him.
 
As I challenge you with these things, I realize that none of us, most certainly including myself, are perfect. You will not be perfect in this regard. We will have times and days when we are more distant from the Lord and seek after other things. Don't be content with this, though. Make it your faith choice to seek after Him wholly and completely in every moment in all things. As you worship Him, adore Him and walk with Him, recognize He is our all in all. Don't be satisfied to just bump along paying minimal attention to our God. Strive each moment after Him who is more than worthy of our complete devotion, worship and praise.