Three types of struggle that men contend with...

1. What man can do to obtain salvation, works, human effort, not trusting God's Divine Grace alone. Man's natural inclination is to do. Man can do nothing to obtain moral holiness or Eternal Salvation of the human soul. Many men struggle to achieve salvation which can never be done. No matter how hard man "tries" he still misses the Grace of God. Grace is what God does. Man is "only" saved by Grace.
2. The "Inner conflict" or "war within man's members" is a struggle that comes to a believer in Christ after the new birth. It's a conflict between the flesh and the work of the Holy Spirit in the life of a believer. This conflict creates a struggle that some may never overcome until they meet with Christ. Other believers "crucify the flesh" or "die to the Old man" and get filled with a Full work of the Holy Spirit that "destroys" the Inner Struggle that so many contend with.
3. The "Outer Conflict" or the outer struggle consists of world pressures, weights, problems of life or other circumstances that hinder the child of God. God doesn't want His children to be burdened with this outer struggle. Christ can deliver man from the pressures of life. How? By simply trusting in Him to meet every need of your life. After all He has power over every condition of life.

Rom 8:32...He that spared not his own Son, but delivered him up for us all, how shall he not with him also freely give us all things?