The Christian life is a life of spiritual warfare and we must be spiritually strong. This begins with the will and choice to be so. Our strength comes from God's word. In our submission to God, we will be made strong.
Eph.6.10-11Finally, my brethren, be strong in the Lord, and in the power of his might. Put on the whole armour of God, that ye may be able to stand against the wiles of the devil.