Lost unregenerate men know nothing of this struggle!

(Frank Hall)

"For the flesh lusts against the Spirit, and the Spirit against the flesh; and these are contrary to one another, so that you cannot do the things that you would." Galatians 5:17

In this one verse the apostle Paul describes the thing that continually plagues every Christian.
We, as the people of God, desire more than anything to love God perfectly, but can't.
We long to cease from sin and ungodliness, but can't.
We strive to worship our God with our entire being, but can't.
We try to do good and honor God in all things, but can't.

Why do we continually do, say, feel, and think things that are evil?
Why are we so hard-hearted, unforgiving, and ignorant?
Why can't we do what we desire most?

It's because we have two natures called . . .
  flesh and spirit,
  sin and righteousness,
  Adam and Christ.

We do indeed believe our God, but not as we would.
We do love our Savior, but not as we would.
We do live for His honor and glory, but not as we would.

Our flesh won't allow us. It always interferes. It keeps us from doing the things that we would. When we would do good — then evil is present with us.
Our most fervent faith, is mixed with unbelief.
Our most selfless sacrifices, are mixed with selfishness.
Our most ardent prayers and supplications, are marred by our infirmities.
Our most spiritual moments, are contaminated by our sickening carnality.
Our meekest hours of submission and dependence on God, are corrupted by our self-will and pride.
Every mountain top experience of spiritual pleasure, is tinged with shameful wanderings within.
Our clearest views of Christ are darkened by error, misconceptions, and preconceived notions.
Even when our hearts seem to be most fixed on God's glory, they are torn between this world and the next.

The reality is, that as long as we live in this world — we will be at war within ourselves! The flesh will not submit to the Spirit — and the Spirit will not submit to the flesh. We will be . . .
  pulled this way one moment — and that way the next;
  believing one moment — and doubting the next;
  praising God in the morning — then murmuring at night;
  seeking God's will today — and our will tomorrow.
As long as we live in this body of flesh there will be a constant struggle within us — a struggle between flesh and Spirit.

Lost unregenerate men know nothing of this struggle! This internal warfare is peculiar to believers. Unbelieving, unregenerate, impenitent, rebellious, lost sinners know nothing of this fight with SELF. They don't loathe themselves as all believers do; they love themselves. They have but one nature — and that is sin, which rules in their hearts supremely. Lost men do not have grace within, to oppose the works and motions of the flesh. All they have is a nature that is dead in trespasses and sin, that walks according to the course of this world.

The struggle doesn't begin within a man, until that man is born of God's Spirit and given the gift of life and faith in Christ.

This war between our flesh and Spirit is best for us. If it were not so, then God would not allow it. God is in control of this fight, and has ordained it for us in His infinite wisdom and grace. This constant battle within our hearts is good for us, because it keeps us looking to Christ — ever seeking Him, His grace, His help, His power. This lifelong fight will make the prize that much sweeter — when Jesus will present us "to Himself as a radiant church, without stain or wrinkle or any other blemish, but holy and blameless!" Ephesians 5:27