Failing With The Lord.....?

Have you ever felt confident that the Lord was with you and yet you were unable to succeed with the challenge at hand?
The first chapter of Judges, verse 19 states that the Lord was with the men of Judah and as a result they were able to conquer the people of the hill country. It's what you would expect, right? But then it says that they were unable to overcome the people of the plains because they (the people of the plains) had chariots of iron. As if to say that the help of the Lord can only do so much but human innovation and military prowess ultimately rules the day. It just doesn't add up against all the other stories of scripture. "Chariots of iron"? That's it? The people of God were no stranger to being outnumbered, outsourced, and overpowered. Consider them facing the Red Sea while being flanked by the most powerful army of the day, and yet the people of God crossed over victoriously because the Lord was with them. I just can't hear the Lord saying this time; "hey I'm sorry, I didn't know that they had chariots of iron, I mean what do you expect from me?". There has to be a more fitting explanation.
I think there is. Iron may be the key. The people of the plains had chariots that were fitted with iron (the newest and toughest metal to date) and it proved to be their reason for a successful resistance. The big question is where did the plains people get their iron? Not from the plains. Deuteronomy 8:9 says that Canaan Land is a place where iron and copper comes from the rocks and hills. Although the people of God were in charge of the hill country, they didn't run out all the inhabitants like they were commanded by God to do. I wonder if the people of the hills kept the plains people supplied with iron. I also wonder if God's people had done all they were commanded to do concerning the people of the hills, would the plains people been able to outfit their chariots with iron in the first place.
I think the greater lesson here is to be careful not to charge God with dropping the ball on our behalf when things are going awry but instead to retrace our own steps to see if there are some areas (seemingly unrelated to our present problem) that we have left unattended that the Lord wants us to give attention to. I'm not saying that we have to be perfect in order for God to work in our behalf and I'm not discounting God's grace for our shortcomings but maybe the reason today's meal seems a little spoiled is because it has been made with yesterday's leftovers.