Having been raised in Fundamentalism I had some exposure to the Deeper Life Movement. Slowly through the years I have seen some of the problems with this line of reasoning and how the Bible approaches godliness from a different way. I am sure most who hold to Deeper Life views are sincerely trying to live godly lives but at the end of the day we want to do things the way God has taught in his Word and not try to improve on them. For this reason I think one of the flaws of the Deeper Life is similar to Hyper Calvinism.
Both ideas want to cast everything into the Lord's hands instead of taking the responsibility God has given us in our service to him. Some Hyper Calvinist don't even believe we are saved by faith in Christ but by the faith of Christ. In some why we are given Christ's faith as our own. Thus some teach that God can save people apart from hearing the gospel since they don't have to personally trust in Christ. The idea behind it is that if we make anything dependent on man or give him a part in anything we take away from the Sovereignty of God. I don't have time to go into all that but basically I believe they go to extremes of biblical teaching to try and resolve problems that aren't ours to resolve.
Similarly Deeper Life proponents teach that if we get out of the way, "let go and let God", then God can work through us. When we try to serve in our own strength and wisdom we just mess things up. This sounds pious but by not being biblically balanced I think it causes more problems than it solves. The issue for me is how is God most glorified by our service. Is his power, majesty and holiness glorified by us emptying our minds and just sitting there waiting for him to do something? Do we point to his glorious person best by being puppets for him to move along solely by his power, putting thoughts into our minds and so forth? Does the Lord want to "drag" us along so it looks like our hearts aren't really in it or we obey merely out of duty. My position is absolutely not.
I believe the Lord is most shown to be worthy of praise and love by us pursuing him with all our heart because we love him supremely. I am not saying that we don't need the energy he gives but it is only when we serve out of a burning desire to serve that we display the fact that he is worthy to be worshiped. To come across as I don't need to do anything but wait on him and just let him do it all sounds a lot like "I don't care that much and am not particularly motivated". At least it seems one could easily fall into a state of lethargy. I am sure this isn't what motivates much of the Deeper Life Movement but they don't seem to be about passion but sitting and waiting.
We don't serve by emptying our minds but by filling it with his Word and then acting on what we know about God; not by waiting for him to "move" us. Again, I am not saying that the Holy Spirit never prompts us but I have seen plenty of Christians "prompted" to do what the Bible never told them to do. I don't think Paul sat around and waited for promptings but it was the God given burden to tell others of his glorious Savior that caused him to pursue God and his work. He didn't wait for God to pick him up and take him where he wanted him to go. God in his providence gets us where he wants us but he mysteriously does so by motivating us through his Word as the Holy Spirit impresses Truth on us. God has "prompted" already in his Word; there is his will, now does your love for him "prompt" you to go out and live it?
The bottom line is that God is most honored when God's people are pursuing life passionately because they love the Lord supremely. Their pursuit is to use life for his glory, not as a way to indulge the flesh. It is our desire to glorify him because he is so wonderful to us. Serving the Lord effectively then cannot be done by simply obeying him because he has told us to. Even the lost can do that to some degree. Even they can sit and wait for him to move them but they cannot be motivated to go out and work for him because they love him.
I think something I said to my people the other day illustrates all this. If I was going to try and motivate them to pray I suppose I could tell them where the Bible commands us to pray and how we should pray and then tell them that you need to pray. It might get them praying for a while but I don't think this is the motivation the Bible uses to New Covenant saints. We might ask ourselves why do I not want to pray? How is it that I don't feel the pressing need to carry all my needs to the Lord and seek his will in all that I do? Why is it that I don't have enough burden for my brothers and sisters in Christ or a burning burden for those I know who are lost that I can't help but pray often for them? What is there about my relationship with the Lord that I don't talk to him often? Get these things right and you will not need the preaching constantly reminding you of your duties.
You see, motivation is everything. The Lord has given us new hearts that we might live in such a way that demonstrates that he is the reason for everything we do. This love works out its salvation with fear and trembling not as puppets but as sons and daughters who have been enabled to serve not just out of duty but because they just can't help themselves.