HOLINESS

Speak unto all the congregation of the children of Israel, and say unto them: Ye shall be holy; for I the LORD your God am holy. 

IMITATION OF GOD (Imitatio Dei)

This commandment is given to the entire community.

God only commands something that we are capable of fulfilling. Failure comes in because we underestimate our abilities.

You do not have to separate yourself from society and go meditate in a forest to become holy. These mitzvot are not for angels. They are mainly interpersonal commandments, such as honoring parents, feeding the poor, not slandering, and not hating in our heart. Being a contributing part of society is a personal obligation. Everyone should aspire to elevate himself, and at the same time aspires to elevate the community. That's why the command to be holy, kedoshim t'hiyu – is written in the plural.

This commandment is given to the entire community. If your being holy enhances your connection to the community, then you are behaving correctly. But if it causes a separation between you and those around you, that is incorrect. Our actions  should always be gauged by what will bring the biggest Kiddush Hashem, sanctification of God’s Holy Name.

Performing altruistic acts without the expectation of reciprocity is one of the greatest godly-attributes. Most religions of the East and West are bogged down by the pre-occupation with what God is or isn’t. For certain, the more we attempt to paint a picture or imagine what He looks like, the more elusive will become the effort to find Him. Emphasizing deed over creed will prove more productive.

The doctrine of the imitation of God is related to the biblical account of the creation of man in the image of God, which acknowledges a resemblance between man and his Creator. Yet man is to imitate God, not impersonate Him (see Gen. 3:5). The main biblical sources for the injunction to imitate God are found in the command to be holy as God is holy and to walk in God's way (Lev. 19:2; Deut. 10:12, 11:22, 26:17).

Man is to be God-like in his actions, but he cannot aspire to be God. This distinguishes the biblical notion from the pagan attempts to achieve apotheosis or absorption in the deity. 
Man is to imitate God in loving the stranger (Deut. 10:18–19); in resting on the Sabbath (Ex. 20:10–11); and in other ethical actions.

"Be like Him. Just as He is gracious and merciful, so be thou also gracious and merciful" 
What is meant is that man ought to walk after [imitate] the attributes of God. Just as the Lord clothes the naked, so you shall clothe the naked. Just as He visits the sick, so you shall visit the sick. Just as the Lord comforted the bereaved, so you shall also comfort the bereaved; just as He buried the dead, so you shall bury the dead"
   
A person should not adhere to a standard of holiness that could have a negative effect on the community.  source:

HOLINESS:

1) The essence of the holiness which every person must strive for is to observe the Covenant in purity. The way to achieve this is by sanctifying the way you speak. You must speak only words of holiness and keep yourself from any lapse into language which is not holy. Then whatever you say will be in `the Holy Tongue,' and through this you will achieve the holiness of the Covenant (19).

2) You must sanctify your mouth, your nose, your eyes and your ears. You must guard your mouth against words of falsehood and anything else which falls short of holiness. You must develop your fear of Heaven in order to sanctify your nostrils. Your ears will be holy when you believe in the Sages and listen to their words. And you must close your eyes and shut out anything which is not good for you to see. The sanctity you attain will bring you perfect understanding, and you will have wisdom, which is God's blessing, and ruach hakodesh, the holy spirit. Another way of sanctifying your nostrils, is if you are humble and patient and do not burst out in anger if someone insults you (The Hebrew expression for anger is a `burning in the nostrils'). The way to sanctify your ears is to be one who is `faithful in spirit and concealeth a matter' (Proverbs 11:13) he is careful not to reveal a secret which there is no need to reveal (21).

3) One who is prepared to sacrifice himself for the sake of sanctifying God's Name will attain peace, and through this the ability to speak holy words of Torah and prayer and to bind the thoughts in the mind to the words which the mouth is speaking. In order to pray with devotion, have in mind that you are willing to sacrifice yourself entirely in order to sanctify God's Name. To achieve perfect prayer, you must pray with a spirit of total self sacrifice (80).

4) It has been proved many times that even the most worthless of Jews, even the sinners of Israel are prepared to sacrifice themselves for the sanctification of God's Name if someone tries to force them to violate the Torah. Each day you should remind yourself that you would be ready to give your life to sanctify God's Name. This is the essence of Israel's holiness. You will then attain peace and be able to pray with true devotion (Ibid.).

5) When you recite the Shema you should say the words in a spirit of total self-sacrifice for the sake of God's Name. Picture in your mind the four death penalties imposed by the Beth Din stoning, strangulation, burning and the sword. You should imagine every detail so vividly that you can literally feel the pain of dying. Thought has a very great power. By imagining yourself dying you can literally come to feel the pangs of death. But be careful not to dwell on these thoughts for too long, because otherwise your soul could literally leave you, God forbid, causing premature death (195).

6) Self-sacrifice for the sake of God brings unity to the worlds above (260).
7) There are certain Tzaddikim who have a very great name and who are known very widely. Yet people hold them in contempt and talk against them. They suffer mercilessly because of this, but it is something they take on themselves in order to sanctify God's Name, and because of it they can save thousands of Jewish souls from slaughter and death, God forbid (Ibid.).

8) Each person has something in his life which is more of a barrier for him than anything else. This is precisely the barrier he has to break in order to serve God. This is his task in life. It is his own way of sacrificing himself. Someone who is very afraid of dying must be more ready than anyone to give up his life to sanctify God's Name (Rabbi Nachman's Wisdom 57).

SOURCE: ADVICE from RABBI NACHMAN