BE HOLY ?

Scripture plainly states that believers are to live lives of moral purity, mirroring the holiness found in Jesus Christ. This involves a conscious, ongoing commitment to resist evil and pursue goodness ...

Therefore gird up the loins of your mind, be sober, and rest your hope fully upon the grace that is to be brought to you at the revelation of Jesus Christ; as obedient children, not conforming yourselves to the former lusts, as in your ignorance; but as He who called you is holy, you also be holy in all your conduct, because it is written, “Be holy, for I am holy.” (1 Peter 1:13-16)

Knowing that we still sin at times, obeying this command seems to be a lost cause. Yet ... we're to bring glory to God by reflecting His character. 

Spurgeon - No one who knows his own heart ever pretends to be perfectly conformed to God’s will. Holiness is a thing of growth. It may be in the soul as the grain of mustard seed, and yet not developed. It may be in the heart as a wish and a desire, rather than anything that has been fully realized - a groaning, a panting, a longing, a striving. As the Spirit of God waters it, it will grow until the mustard seed shall become a tree.

The Holy Spirit's ongoing work of sanctification is evidenced by an unquenchable thirst for 'holiness'. So how do you pursue it? 

Both the desire and the power to be 'holy' come from the Lord. We are to surrender to (and cooperate with) that which He does within us.  

Some read this verse as the role man plays in his own salvation ... Follow peace with all men, and holiness, without which no man shall see the Lord. (Hebrews 12:14) 

But that runs contrary to this passage ... For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast. (Ephesians 2:8-9)

So Hebrews 12:14 actually means 'put feet to your faith'; otherwise, unbelievers will not 'see the Lord' in you ... only hypocrisy.  

You are already considered 'holy' if Christ's righteousness has been credited to your account by faith in His finished work. He desires that you walk in the light as He is in the light.

Don't be one who 'knows more than he practices' ... more doctrine in your head than holiness in your life.