...except that it be given him from heaven.

"A person can receive nothing except that it be given him from heaven."--Jn. 3:27

Most people really have a hard time accepting gifts.  Most feel the need, when receiving a gift, to do something in response, in effect paying for the gift (which would make it no longer a gift!).  Others have no problem accepting gifts--they receive the gift, say "thank you", and move on the enjoyment of said gift.
The Gospel meets both types of people (and I do believe most people are one or the other).  The reason the Gospel meets both is that it says that all is dependent upon the grace of God, along with the fact that it says we're responsible creatures.  This would mean that even our responding positively to God's command is also a gift, "so that he who boasts would boast in the Lord" (1 Cor. 1:31).

After John the baptizer says what he says in John 3:27, Jesus later sheds even more light on it.  In context of speaking with his disciples about their bearing good fruit for him, he says, "As the branch cannot bear fruit by itself, unless it abides in the vine, neither can you, unless you abide in me..." almost immediately adding, "..for apart from me you can do nothing" (15:4,5).  Jesus' point is very clear--we can do nothing apart from Him. 

This means that not only is my good fruit a result of His life in me bearing good fruit, but my very faith in the first place is a result of God's grace towards me (see 1 Cor. 15:10, Eph. 2:8), which means that my being grafted into Him the Vine is also a result of God's grace towards me (see Rom. 11:17-21).  We remember Jesus' sobering reminder to the disciples lest they become prideful, "You did not choose me, but I chose you, and appointed you that you should go and bear fruit and that your fruit should abide" (Jn. 15:16). 

This shouldn't be hard for Christians to understand--in fact it should be readily accepted.  Unfortunately it is hard to accept and believe by many American Christians who are more American than they are Christian; we so struggle with finding out complete identity in Christ because our culture has told us to "believe in ourselves" and "achieve our dreams", which has bred a people who desperately want credit for what they do.  Those in Christ should know of no such thing--the whole POINT of God's work in Christ is God's glory and not ours.  He testifies to it in the Prophets (Is. 12:3-4--"In that day you will draw water from the wells of salvation, and you will say, 'Give thanks to the Lord..make known his deeds among the peoples"; Ezek. 36:27,38--"I will put my Spirit in you and cause you to walk in my statutes and obey my rules...(and) then they (cities, nations, etc.) will know that I'm the Lord"), and Peter testifies to it in his epistle (1 Pet. 2:9--"You are a chosen race, a royal priesthood, a holy nation, a people for his own possession, that you may proclaim the excellencies of him who called you out of darkness".)  The whole point of the work of Christ is for us to exalt the glory of God and make known HIS deeds--because man truly can receive nothing unless it's given him from heaven, and this includes faith, obedience (see Ezek 36 passage), and good fruit. 

We have a sovereign God who "works all things according to the counsel of his will" (Eph. 1:11), and He has united us with His risen and resurrected Son who sits at His own right hand in heaven.  My prayer today is that you understand that God is to be glorified because everything, from you fruit to your obedience to your faith has been accomplished by Him in the first place anyways--therefore it's insanity and foolishness to want to take any credit.  Those in Christ won't--because those in Christ know that they're in Christ as a gift given them from heaven.  When God is glorified, then your heart will fill up with thanksgiving, and you will be filled with joy.  Only this time, it will be joy as coming from the Father, so it will be complete, instead of the half-joy that is rampant among the Church today.  And this true joy from God will be for our good, and His glory.