How to live in the world but not be of the world?

Psalm 3:4-8 KJV

[4] I cried unto the Lord with my voice, and he heard me out of his holy hill. Selah. [5] I laid me down and slept; I awaked; for the Lord sustained me. [6] I will not be afraid of ten thousands of people, that have set themselves against me round about. [7] Arise, O Lord ; save me, O my God: for thou hast smitten all mine enemies upon the cheek bone; thou hast broken the teeth of the ungodly. [8] Salvation belongeth unto the Lord : thy blessing is upon thy people. Selah.

Psalm 4:1-8 KJV

[1] Hear me when I call, O God of my righteousness: thou hast enlarged me when I was in distress; have mercy upon me, and hear my prayer. [2] O ye sons of men, how long will ye turn my glory into shame? how long will ye love vanity, and seek after leasing? Selah. [3] But know that the Lord hath set apart him that is godly for himself: the Lord will hear when I call unto him. [4] Stand in awe, and sin not: commune with your own heart upon your bed, and be still. Selah. [5] Offer the sacrifices of righteousness, and put your trust in the Lord. [6] There be many that say, Who will shew us any good? Lord, lift thou up the light of thy countenance upon us. [7] Thou hast put gladness in my heart, more than in the time that their corn and their wine increased. [8] I will both lay me down in peace, and sleep: for thou, Lord, only makest me dwell in safety.