Your job is to be faithful, God will produce the fruit.
Even if God chooses not to bear fruit in my labor, it is still worth doing. Regardless of fruit, my faithfulness glorifies God, and that is enough for me.
How much do I need to do to be faithful? That is the wrong question to ask. That’s like asking “how faithful do I need to be in my marriage?” When I look rightly at what God has done for me and who he is, I cannot help but desire to give him myself. Jesus calls me to pick up my cross and follow him; to hate any one or any thing in comparison to loving him; to sell all that I have and follow him, because he is worthy! I cannot ask “how much” or “how far”. When he says “follow me”, there is no “this far”, no “but”, no “until”. “He who puts two hands to the plow and looks back cannot be my disciple”. All he says is “trust me”. That’s exactly what it means for Jesus to be Lord. My “yes” is on the table.
So how faithful do I need to be? As faithful as I can be, with everything I am and have, all my life. This sounds daunting at first. But remember, God sees our hearts. He knows our starting place; our weakness. Of the two servants in the parable of the talents in Matthew 25, one produced 5 talents from the 5 he began with and the other 2 talents from 2. Which was more faithful? The Lord affirmed both the same: “Well done, good and faithful servant.” It was all about what they did with what they had.
Faithfulness produced out of fear is worthless. It may look impressive externally, but that which does not proceed from faith is sin (Romans 14:23). Real faithfulness must be motivated by the grace that we have been given in Christ. As we see the glory of God in the gospel, our hearts will well up with an eager desire to be used by God, and, as we do good works for his glory, we will be filled with joy. Our greatest joy is found in serving our Lord.
 For what is our hope or joy or crown of boasting before our Lord Jesus at his coming? Is it not you?  For you are our glory and joy.
Faithfulness produces humility. When we hear “well done”, our response will not be pride, but humility. God is the one who worked in us to give us the opportunity and power to be faithful. “For we are his workmanship, created in Christ Jesus for good works, which God prepared beforehand, that we should walk in them.” Our faithfulness should not be impressive in our own eyes, for it is the only right response to such a great love. For that reason, we will take any crowns we receive and give them back to the Lord, for he is the one who works and wills for his glory.