Some Sufis define wara' as the conviction of the truth of Islamic tenets, being straightforward in one's beliefs and acts, being steadfast in observing Islamic commandments, and being very careful in one's relations with God Almighty. Others define it as not being heedless of God even for the period of the twinkling of an eye, and others as permanently closing them-selves to all that is not Him, as not lowering oneself before anyone except Him (for the fulfillment of one's needs or other reasons), and as advancing until reaching God without getting stuck with one's ego, carnal self and desires, and the world.
Always refrain from begging from people,
Beg only from your Lord Who is the All-Munificent.
Renounce the pomp and luxuries of the world
Which will certainly go as they have come.
We can also interpret wara' as basing one's life on engaging in what is necessary and useful, as acting in consciousness of the real nature of useless, fleeting, and transient things. This is stated in the Tradition: It is the beauty of a man's being a good Muslim that he abandons what is of no use to him.
The writer of the Pandname, Farid al-Din al-Attar, explains this principle in a very beautiful way:
Wara' gives rise to fear of God,
One without wara' is subject to humiliation.
Whoever uprightly follows the way of wara',
Whatever he does is for the sake of God.
One who desires love and friendship of God,
Without wara', he is false in his claim of love.
Wara' relates to both the inner and outer aspects of a believer's life and conduct. A traveler on the path of wara' must have reached the peaks of taqwa; his or her life must reflect a strict observance of the Shari'a's commands and prohibitions; his or her actions must be for the sake of God; his or her heart and feelings must be purged of whatever is other than God; and he or she always must feel the company of the "Hidden Treasure."
In other words, the traveler abandons those thoughts and conceptions that do not lead to Him, keeps aloof from those scenes that do not remind one of Him, does not listen to speeches that are not about Him, and is not occupied with that which does not please Him. Such degree of wara' leads one directly and quickly to God Almighty, Who declared to Prophet Moses: Those who desire to get near to Me have not been able to find a way better than wara' and zuhd (asceticism).
The abstinence known by humanity during the Age of Happiness was perfectly observed by the blessed generations following the Companions, and became an objective to reach for almost every believer. It was during this period that Bishr al-Khafi's sister asked Ahmad ibn Hanbal:
O Imam, I usually spin (wool) on the roof of my house at night. At that time, some officials pass by with torches in their hands, and I happen to benefit, even unwillingly, from the light of their torches. Does this mean that I mix into my earnings something gained through a religiously unlawful way? The great Imam wept bitterly at this question and replied: Something doubtful even to such a minute degree must not find a way into the house of Bishr al-Khafi. 
It was also during this period that people shed tears for the rest of their lives because they had cast a single glance at something forbidden, and people who vomited a piece of unlawful food that they had swallowed in ignorance wept for days. As related by 'Abd Allah ibn Mubarak, a great traditionist and ascetic, a man traveled from Merv (Afghanistan) to Makka in order to return to its owner an item that he had put in his pocket by mistake. There were many who gave life-long service to those to whom they thought they owed something, such as Fudayl ibn 'Iyad. Biographies of saints, such as Hilyat al-Awliya' (The Necklace of Saints) by Abu Nu'aym al-Isfahani, and al-Tabaqat al-Kubra (The Greatest Compendium) by Imam al-Sharani, are full of the accounts of such heroes of abstinence.
 Qushayri, al-Risala, 111.