First, let’s define “sin.” Scripture describes the steps to sin in James chapter 1.

(1)    A person is enticed. Something that is appealing to a person’s unique sin nature (resident in their lower mind) catches their attention. [Not a sin, yet. Wait for it…]

(2)    Next, their sin nature conjures one or more sinful activities (mental or behavioral) related to the enticement and passes possible activities up where the upper mind may then dwell on the possible sinful actions related to that enticement. [Not a sin, yet. Wait for it…]

(3)    Then, the upper mind decides to break from the ongoing guidance of God provided through the indwelling Holy Spirit and embrace the sinful activity as a course of action. Once embraced (not yet performed, but only embraced), it becomes sin. The person has not yet engaged in the sinful activity, only embraced it as a course of action. THIS IS WHERE SIN HAS OCCURRED. It is not the embracing itself that defines the sin, but that the upper mind must deny God’s leading to embrace the sin.

(4)    The consequence of this going-your-own-way is a break in the on-going relationship/fellowship a believer enjoys with God. Not a break in the "positional" relationship—you are still a child of God destined to heaven, but a strain in the practical relationship not unlike that of a parent and child (a disobedient child, but still your child). This strained relationship is referenced in Rev.3:20, where God seeks to re-establish something the believer has interrupted.

Now, let’s describe “faith.” For the believer in this age, faith is also defined as the antithesis of sin (Rom.14:23). Just like sin:

(1)   We can discern that faith begins with a belief about something God has said (like the enticement in the sin process). 

(2)   After consideration, the belief is then personally embraced as a course of action—this is faith. Faith is not a verb, mind you; it is an internal embracing of a belief as a standard for later behavior. The behaviors result from the faith, but are not faith.

(3)   The result of this faith is spiritual life (and growth)—the opposite of spiritual death described as the consequence of sin in James 1. This is why it is said that one can be a believer, but weak in faith (Mat.8:26; Acts 14:22; Rom.12:6; 2Tim.1:5). They believe, but have not embraced the belief as the genesis for a behavior.

Can you see now how faith and sin are mirror images?

Now, a word about your old sin nature (OSN).  The OSN was inherited from Adam and—while not sin itself—is your autopilot toward sin. If left to itself, it will always tend to guide you toward sin. However, it is subservient to direction from the upper mind. That is why Scripture says that God will never allow you to be tempted beyond that which you can withstand. That is, the OSN is easily enticed and very good at recommending sin to the upper mind, but it is still the upper mind that must make the unencumbered decision to embrace the sin as a course of action . Both prior to and after salvation your sin nature acts to produce two kinds of mental or physical behavior (or works) as directed by the upper mind. One is human evil while the other is human good.  The evil output of the OSN is easily recognizable.  Human good is represented by those thoughts and actions that, while on the surface appear to be noble, true and righteous, but actually are self-directed. As self-directed, these thoughts and actions deny God's guidance and fall short of God's perfect holiness and, thus, are still deemed as sin. Recall that "holiness" means "set apart for God's use." Denying God's guidance to engage in a self-directed, apparent act of righteousness leaves God out of the equation and, therefore, must be sin. This is why all of our 'works' when we are unsaved—even the noble ones—are considered "filthy rags" to God (Isa.64:6).  All of these works by a less-than-holy human spirit are sin when compared to God's perfect holiness and guidance.

As an immediate consequence of salvation, each believer is permanently indwelt by the Holy Spirit. The Holy Spirit takes up residence in the upper mind and effectively locks out "possession" by Satan or his minions. External Satanic influence is still possible, but the indwelling Holy Spirit never allows the external influence to force itself on you.  Remember, the Holy Spirit will never allow your OSN to be externally tempted beyond your capability to resist. [That's not to say, that you won't routinely give in far short of your capability to resist.]

Once on board, the Holy Spirit acts to provide an available (yet never forced) option to control by your human spirit. For someone who is saved, there is the option by the human spirit to yield to God's sovereignty and direction as provided by the indwelling Holy Spirit. Yielding to God—while probably not your first or natural inclination—allows the Holy Spirit to impose God's will through your human spirit to your lower mind and body so that the resulting 'work' or effort produced is divine good. Or, one could elect never to yield control to the indwelling Holy Spirit and, thus, never produce any divine good.