Can you be following God's plan and He still not be on your side?

And it came to pass, when Joshua was by Jericho, that he lifted his eyes and looked, and behold, a Man stood opposite him with His sword drawn in His hand. And Joshua went to Him and said to Him, “Are You for us or for our adversaries?” So He said, “No, but as Commander of the army of the Lord I have now come.” And Joshua fell on his face to the earth and worshiped, and said to Him, “What does my Lord say to His servant?” Then the Commander of the Lord’s army said to Joshua, “Take your sandal off your foot, for the place where you stand is holy.” And Joshua did so.
Joshua 5:13-15(NKJV)


It's kind of funny when you think about it. Joshua was in this place having recently been sent out of the desert and across the Jordan by Moses. This great leader that Joshua had been following for most of his life, and who was now dead. Now suddenly he is instructed to lead this nation... this nation of bickering, whining, complaining, and totally unprepared people who had never known a day of real war in their lives to conquer all of this land and all of these other nations. He has seen God working with him, but he has no idea what he is doing. He has always been a follower, but that is no longer an option for him anymore.
He knows that this is what God has for His people, but he has no idea how it will happen. He's walking around one day scouting out Jericho and trying to figure out what to do next when suddenly he sees this guy facing him with a sword in his hand. This guy was probably prety intimidating looking and probably had a really powerful presence about him. Joshua sees this guy, obviously a warrior standing there looking at him with his sword drawn. Joshua ch 1 alone has four different instances in which God tells Joshua to be strong and courageous. In fact in verse 9 He says “Have I not commanded you? Be strong and of good courage; do not be afraid, nor be dismayed, for the Lord your God is with you wherever you go.” (NKJV) So Joshua is obviously prone to being a little timid or afraid. Yet he goes right up to this guy, this warrior, and asks him plainly, "Are you for us or for our adversaries?" And yet this warrior does not give him an answer that Joshua is expecting. Instead of pleadging his support of Joshua and the Isrealite people or threatening and cursing him saying that they would indeed destroy this invading hoard, instead this warrior tells Joshua, “No, but as Commander of the army of the Lord I have now come.”
So, the question posed is, "Can i be following God's plan and He still not be on my side?" the answer seems to be a resounding "Yes". The Commander of the army of the Lord makes it clear that He is not there to serve Joshua, but that Joshua must continually serve the Lord. We see this dynamic played out in Joshua 7 where Joshua and the Israelites attack the city of Ai and are driven back due to the sin of one man.
So what does this mean for me? Basically this means that, even when i have been given a goal and instructions by God, i still must seek him daily and in all things to ensure that my life and my plans line up with His. It is too easy for us sometimes to feel that we have a mandate from God, and in the process to try to reach His goals through our own plans and will.

Trust in the Lord with all your heart,
And lean not on your own understanding;
In all your ways acknowledge Him,
And He shall direct your paths.
Proverbs 3:5-6 (NKJV)