Question: Does God focus more on the sin, or on what the believer is doing for God? Should I worry about sin, or worry about serving God?
Answer: I will be happy to respond to your question today, especially because it shows your win-win attitude. You want to know which would please God more, avoiding sin or serving him directly? What a dilemma! I wish that every Christian would ask that same question! However, we need to work through a few technical issues before we proceed, so please bear with me for a paragraph or two.
I see the parallelism in your question, so I think that I understand what you are asking by the phrase Does God focus..., but I cannot let it pass unchallenged, because (in purest terms) God does not focus. God is omnipotent and omnipresent, that is, he has the power to do all things and he is at every place at the same time. As such, he has no need to focus. We do, but that is because we can only manage a few things at the same time. We divide (apportion) our time and energy among only the important tasks because we do not have enough resources to perform them all. God, on the other hand, does not need to divide himself since he is limitless. He knows every detail of our sins and every detail of our service. He is all knowing, all observing and all attentive to all of us all of the time. As you can see, focus is not an issue with him.
I am not saying that God is not attentive. In fact, the Bible uses phrases like "the eyes of the Lord" about 170 times. God does not have a physical body, and we know that he does not need to scan the horizon to find out what's going on in the world. However, he does want us to know (through the agency of anthropomorphism) that he has an attitude of oversight, and we see him again and again "seeing"—sin mostly but occasionally righteousness. Want to know what God is looking for? He is actively looking for that perfect heart.
“For the eyes of the LORD run to and fro throughout the whole earth, to shew himself strong in the behalf of them whose heart is perfect toward him...” (2 Chronicles 16:9, AV)
As for the first part of your question, he sees our sin but he looks for our service. As for our sin, we have a high priest in Jesus Christ who makes continual intercession for us (Heb. 7:25). We should confess our sins before him (1 John 1:19). As for our service, we have consecration, the dedicating of ourselves to him. God deals with the sin but we must deal with the service. One is not better or more important than the other. They are both necessary for the congruent Christian life, but service is, by its nature, the aspect that most requires your engagement.
The best defense is a good offense, although a cliché, is the best way to approach the second part of your question. As Christians, we should put the greatest portion of our energy into the positive aspects of our Christian lives, using that as the primary method to avoid sin. We should not spend our primary energies trying to avoid sin, because that causes productive life to grind to a halt pretty quickly. I know that we are going to sin—that's a guarantee. However, if we focus on serving God we will commit those sins as earnest klutzes rather than as idle worriers. Yes, they are both sin, but I think the first type reveals a truer heart.
We cannot serve God, however, unless we belong to him. Many people profess Christ, but a true Christian is a child of God (2 Cor. 13:5). We must be born again as new creatures (John 3:3). Only then are we qualified to work the works of God (Mat. 7: 21-23). To help with this work, we born again Christians have the Holy Spirit of God living within us. He teaches concerning the Christ, illuminates Scripture and gives us discernment in life. Through his agency we may effectively pray, read the Bible and fellowship with other believers. When we feel that those three activities have become the most important parts of our lives, then sin will be at a minimum—and again, this will not be by focusing on preventing sin per se, but by focusing on God and enjoying a balanced spiritual life.
Our sin saddens God (and it should sadden us) but it can never send a child of God to hell. We are eternally secure in our salvation (Rom. 8:35-39). However, sin can still wreck our lives. It can disqualify us from service altogether, so we should not ignore it. We should know what is and where it is—and even do the occasional inventory to see what we can clean up (1 Thes. 5:21). That is only sensible behavior in this sin-filled world, but this should not be our primary focus. Our primary focus should be to spread the Gospel.
I have noticed a parallel principle in day-to-day life. We tend to go where we're looking. Take driving a car on a bad road, for instance. A skilled driver keeps his attention on where he wants the car to go. Now, he knows that there are hazards very near the edge of the road, but he does not turn his head to look at them. Instead, he keeps his attention on the road in front of him because, whether or not he knows this consciously, he will steer the car wherever he places his gaze. The Christian life is no different. Do not stare at the road hazards. Stare at Jesus Christ.
In conclusion, sin waits very near to us, and it is ready to make us pay for the slightest moment of inattention. But we should not take our eyes off the mission that God has given us. Yes, be aware of (and avoid) sin. We certainly must address that with some of our resources, but remember—we're on a budget. Therefore, let us spend our primary energies on serving God. And hey—if we are serving God with the proper vigor, we should be be too tired for sin anyway.