The term Taqwa is often translated as 'piety' or 'God-fearing', but a better equivalent would be 'God-consciousness'. It is considered to be the essential quality of a believer. Taqwa of a believer should illuminate through all facets of his/her life, just like a bright light would shine through all openings of an empty house in an empty field in a dark night. Taqwa, when coupled with Imaan (faith), makes a well-rounded believer. Taqwa goes hand in hand with Imaan; one cannot be complete without the other, and vice versa.
Taqwa is the state of hyper-vigilance against falling into sin in negligence. It is the idea that a believer is always on guard and is perpetually alert of not committing any action that would earn the displeasure of the Almighty. It is the state of preparedness of anticipating a situation where one might be coerced into doing Haram, and as a result of this readiness, to avoid and stay out of that Haram. In its higher forms, Taqwa is the fear of not of not taking the best path towards Allah's Pleasure and His Grace.
Taqwa is often translated as 'fear of God', but the real essence of Taqwa is being hyper-vigilant and the 'fear' of doing Haram out of neglect of Allah's orders. It is the state of consciousness to be mindful of Allah at all times and achieve His maximum pleasure at all times. Therefore, any such qualities of a person that would make him forgetful of Allah are detrimental to his/her Taqwa. The love of this world, greed, hatred or enmity towards a fellow human, pride, etc. are all examples of such traits that hurt a believer's Taqwa. As a result, the more cognizant a believer is, and more alert (s)he is in protecting him/herself from such detrimental traits that would make him/her forgetful of Allah, the better his/her Taqwa or 'God-consciousness' is.
The consciousness that Taqwa implies is a reverential consciousness. The state of alertness when one is in awe and admiration of something or somebody. Imagine you met your lifelong role model, how attentive to their every need would you be? You would notice all their little quirks and nuances, their body language, behavior, what irks them, and what makes them happy. If they indicated that they want something, you would rush to get it done in the best manner possible and do it in a way that would make them most happy. You would suppress any internal resistance inside you that would keep you from doing the best job. You would be 'fearful' in becoming complacent to their need and not doing your best for their satisfaction. A parallel example is if you were in the company of someone you deeply and intensely loved. You would anticipate and plan ahead to make them feel as comfortable and at ease as possible. You will always be alert and vigilant and will think ahead so as to avoid any situations or scenarios that would make them even remotely unhappy. All your efforts will be focused in keeping them happy and comfortable as humanely as possibly. If they called upon you, you would drop everything you would be doing to attend to their need immediately. Also, you would be so conscious of the surroundings and especially vigilant to how you act, what you say or do in their presence, so that they don't get turned off in any way.
Taqwa implies a similar sense of alertness, consciousness and vigilance towards the Pleasure and Mercy of Allah. To be constantly aware of what pleases or displeases Him and to ensure all our efforts are to make Him most happy and gain His maximum Pleasure. Taqwa means to rush in acting upon the orders of Allah and to suppress any inclinations that would prevent us from completing the tasks in its best form. But Taqwa goes a step further than the love for a beloved or the admiration of a role model as outlined above. To be hyper-vigilant in the presence of a beloved or a revered person may be commendable, but the essence of this endearment is measured if the level of alertness is same in their absence. Allah is not physically present and visible to our eyes: He is Haadhir (present) but Gha'ib (unseen). What makes Taqwa so challenging and rewarding is the idea of expressing this level alertness and attentiveness to Allah in His 'absence', when He is not visible.
As such, Taqwa cannot be classified simply as "piety" or "fearing God"; rather, it's much deeper and intricate than that. A person who has Taqwa is a Muttaqi (pl. muttaqin). A Muttaqi demonstrates this constant state of endearment throughout his/her actions in every facet of his/her life. (S)he reduces all the obstacles that prevent him/her from dedicating everything to Allah. (S)he minimizes the distractions and all the 'noise' in his/her life that drown out his/her awareness of Allah. It is also said that God manifests Himself in the silences of the soul, and if a person has a lot of noise – desires, diseases of the soul, Haram passions, etc. – (s)he will never be able to feel the presence of Allah in his/her soul. The soul will never be awakened to the reality of the Eternal Being, because it is cluttered and clogged with all other pursuits. In order to hear His whispers, one has to be silent. If a person never stops talking, they will never be able to properly listen to Allah, as they are going to be preoccupied with their own complaints. They will never be able to reach a point of internal peace whereby they can speak to Allah. Just like the depths of a pond become invisible when the surface water is experience rough motion (waves, etc.), our own depths will remain invisible if we don't calm the surface of the soul. That is to say, until one empties and removes all distractions of this world and cleans the diseases of the soul, (s)he will not be able to deeply connect with Allah.
As the Holy Qur'an says, "He (Allah) is with you wherever you are." (57:4) He is neither absent, nor is He missing. It is rather our consciousness and our awareness – our Taqwa towards Him – that is absent and missing. He is with us along every step of the way, but we are aloof of Him at every moment. Only if we tuned in to Him, became conscious of Him, and awakened our souls to Him can we experience His manifestations with our own souls. (41:53)
These are the qualities of the Muttaqeen. We pride ourselves in being followers of Imam Ali (peace be upon him), who is also called Imam al-Muttaqeen – Leader of the God-Conscious Ones. If we truly want the Imam to accept us in his following, we have to cultivate the traits of the Muttaqeen in our lives. We have to be ever-alert and hyper-vigilant of the presence and pleasure of Allah in all aspects of our daily lives. Then we can start approaching the position and can emulate the Imam, where he says, "I did not do anything in life except that I saw Allah before it, within it, and after it."