The you in this verse is Gideon and the speaker is God. God had Gideon go down to the enemy's camp and hear what they were talking about. God had put scary dreams into the men's heads about Gideon defeating them. God was already preparing the enemy to lose. All Gideon had to do was obey and go in there and he would have the victory.
God does the same for us. He prepares the way and let's us be a part of the victory.
It's like when I make sugar cookies with my young children. I make the dough. I bake them. I make the frosting. And then they frost the cookies with the frosting I made and the cookies I baked. They were given a part, the best part but I did the work. If they are really young they will tell people, "I made cookies" when all they did was frost them. I of course don't care cause I know what really went on.
But when it comes to spiritual things and big situations in life, if we take the credit we are putting people's eyes on us rather than God. God makes it so the victory obviously came from Him so people will look to Him and depend on Him. When we take the credit we take away an opportunity for them and God.