First the background, then the application.
What is Sin? Sin is when we fall short of God and what he wants. (Rom 3:23).
So because of sin, the world is in misery? Yes, sin separates us from a perfect, holy, righteous and just God. Which means we are separated from perfection. We no longer have a perfect relationship with God, ourselves, each other and the earth. These lead to loneliness (separation from God), self-loathing and illness (separation from ourselves), hatred, envy and war (separation from others) and natural disasters (separation from the earth).
So can we be good without God? No. Because God is holy, righteous and just – in God’s eyes “good” is perfect. And part of performing a “good” is to have the right motive. So if any of our actions does not have the right motive (which is doing something out of love for God) then is still sin. Like if someone only feeds the hungry to impress their girlfriend, the motive is wrong because it’s done out of selfishness. So without proper motive, we, in essence, become slaves to sin (Rom 7:14-25, 8:7-8).
So then how can we be good? Because God is not only just but also love, he sent Christ to pay for the sins of those who have faith, therefore, repairing our separation from him. It releases us from our slavery to sin and allows us to love God, therefore giving us the right motive in our actions, allowing us to perform works pleasing to God. (Rom 7:21-25, Heb 11:6)
So now there is a battle inside us between our old sinful nature and the new spiritual nature? Yes. Paul says is best when he says, “For I do not do the good I want, but the evil I do not want is what I keep on doing… For I delight in the law of God, in my inner being, but I see in my members another law waging war against the law of my mind and making me captive to the law of sin that dwells in my members.” (Rom 7).
So what am I supposed to do knowing there’s this battle? You fight the battle. First by knowing, the war has already been won and second by knowing that God himself is helping you fight this battle by growing your strength, by making you more like Christ, which is called sanctification. (Rom 8:28-29, Jam 1:2-4).
So yes, your kids, spouse, friends and coworkers are essentially bags of sin. The entire purpose of life is to Love God and Others, that’s it. So for you to help others love God and others more – you are essentially helping them sin less. To do this you must understand their sinful nature, you must understand the battle. Then you must put a plan in place. First by teaching by example how you love God and love others – meaning the first step is to get your act together if you are to teach your family by example, then work outwards to others.
If I’m going to heaven anyways, what eternal effects will there be from how seriously I take this battle? For some reason, Christians think there’s no difference between rewards in heaven. Yes, we will all be in perfect happiness, but we will have differing roles and responsibilities. What we do now affect our eternal lives in heaven.