The NIV says it a bit differently......

Simon answered, “Master, we've worked hard all night and haven't caught anything. But because you say so, I will let down the nets.”

We had a missionary today at church preach on this passage of scripture. He spoke about Jesus getting involved with the disciples and getting right in their boat trusting to bring them to the place where they could take His message to the world.
 
I got grabbed however by those words in red above.

They had fished all night, knew the business and didn't get a thing. What he asked them to do was REPEAT an effort on their part and go back out.

Ever heard a burden or had a burden and you hear or you say "I already prayed over this before"

A healing, finances, relationships, any burden...ever think no point in going back out and do it again, because you are tired and know nothing will come of it...in the natural?

Well, Lord, because YOU say so......

Luk 5:6

And when they had done this, they caught a great number of fish, and their net was breaking.

Obedience brought blessing.