". . . but the hill country shall be yours, for though it is a forest, you shall clear it and possess it to its farthest borders. For you shall drive out the Canaanites, thtough they have chariots of iron, and though they are strong." - Joshua 17:18 (see whole chapter for context)
Now, we all know what happened in history. These people of long ago failed to attempt to claim the promise. They didn't fail in their attempt, but they failed to attempt. It is NOT too hard to walk in and fight for what God has promised us. We are assured success, in fact, but only if we make the attempt. God help us to try!