Joshua 8:26. "For Joshua did not draw back his hand, with which he stretched out the javelin, until he had utterly destroyed all the inhabitants of Ai." 

In stretching out the javelin, Joshua was following the Lord's command, He had instructed Joshua to "Stretch out of the javelin that is in your hand toward AI, for I will give it into your hand." (Joshua 8:18). Even though the conquest of Ai was a rout, with there not being a time when it seemed the Jews would not be successful (Joshua 8:19-23), Joshua never lowered his hand, he held the javelin toward Ai until the battle was completely won.

We sometimes feel like giving up when we are struggling. As we carry our crosses, sometimes they can feel so heavy, or seem so pointless, that we think "This can't be right, this can't be something God wants me to do." Or, as I tend to do, we can be certain God is asking us to do something, but when we start encountering setbacks, we begin to wonder if we were wrong and maybe it is not God's will. But in reading this verse, it occurs to me that sometimes we are tempted to give up not out of a sense of failure or difficulty, but of anticipated victory, and that is just as wrong.

When Joshua saw how easily the Jews were conquering Ai, he could have lowered his arm, assuming that he had done as much as needed, since victory seemed assured. We don't know what it would have happened if he did, perhaps the conquest would have been lost, or not as easy. But he "did not draw back his hand" until Ai was fully defeated, even though that defeat seemed guaranteed from pretty early on.

So while I certainly have to remember to keep doing what God asks of me, even if it seems like nothing is changing, even if my difficulties or sufferings increase, and even if things don't go the way I think they should; I also have to remember to keep doing what God asks of me when I see immediate positive results! Those situations present a more subtle temptation to quit. I may be tempted to think that I just had to get the ball rolling, and now I can rest, in fact I'm certain I've done this at times.

It is rarely, if ever, the case with God that we are only meant to get things started and then withdraw or step back. He gives us abilities and instructions that we should never stop using and following, whether the results seem good or bad. This does not mean we can never "lower our arm", but we will know when the thing He was accomplishing through us is complete, just as Joshua knew when the conquest was total, and only then lowered his arm.