What is real dharma / religion? Why there is quarrel in the name of religion?

Dharma is sometimes translated as religion,but that is not exactly its meaning. Dharma actually means that which one cannot give up, which is inseparable from oneself. There is nitya-dharma and anitya-dharma, eternaldharma and temporary dharma. Every living or noliving object around us , has its eternal nature or dharma. That nitya-dharma cannot be separated from the an object.
Srila Prabhupada gives an example: the warmth of fire is inseparable from fire. Therefore,warmth is the nitya or eternal dharma of fire. Another example is water. Liquidity is the eternal dharma of water. Sometimes if there is freezing cold then water turns into a block of frozen ice. But that is not its eternal dharma. The eternal dharma of water is liquidity. When the temperature rises again, it melts. The ice is temporary, anitya-dharma.
The body has its dharma, the mind has its dharma, and the soul has its dharma. Sense gratification is the dharma of the material body. The dharma of the mind is sankalpa and vikalpa, accepting something and rejecting something. Thinking, feeling, and willing is the dharma of the mind. We,living entities are soul,atman.We are neither body nor mind.

Dharma of the Soul

In chapter eighteen, verse sixty-six, Krishna has given His most concluding, confidential instruction in the Bahgavad Gita: sarva-dharman parityajya mam ekam sharanam vraja i.e.“Abandon all varieties of dharma and just surrender unto Me.” That is the dharma of the soul, i.e atma-dharma. It is not the dharma of the body or the dharma of the mind. You are soul, and your eternal dharma is as a servant of God or Krishna,i.e.Krishna Dasa. If you donot become a servant of Krishna then you will be forced to become a servant of maya i.e.maya dasa.

Sri Chaitanya Mahaprabhu said, jivera svarupa haya Krishnera nitya-dasa. As a jiva, your svarupa, your constitutional position, is as an eternal servant of Krishna. [Cc. madhya 20.108] This is parama-dharma, bhagavata-dharma, the eternal dharma of the soul.
It is not Hindu dharma or Muslim dharma, or dharma of the black or dharma of the white. It is not Australian dharma, American dharma, Japanese dharma, Chinese dharma, or Indian dharma. No.Dharma is one. Dharma is to become God's/Krishna’s servant and completely surrender unto His lotus feet.That is the only dharma. You may be Australian, African, Chinese, Japanese, or Indian,whatever . but you are all souls.

If society can understand what is real dharma, eternal dharma, then there will be no quarrelling on the matter. Everyone will be satisfied. But they donot try to understand this subject. Therefore quarrelling goes on in name of dharma/ religion.

As explained by SRI SRIMAD GOUR GOVINDA SWAMI MAHARAJA

How to break bad habits?

The first step in overcoming this material conditioning is of course to recognize the bad habits themselves. This recognition should be accompanied by sincere regret followed by firm resolve to give up the habit. But often we find that despite being aware and regretful for their habits, many people are unable to avoid their sinful tendencies, because of the lack of proper effort. It takes great commitment sustained over time to accomplish the result.

Srila Rupa Gosvami gives us the formula for accomplishing it:(Nectar of Instruction verse 3)

utsahan niscayad dhairyat
tat-tat-karma-pravartanat
sanga-tyagat sato vritteh
shadbhir bhaktih prasidhyati

i.e.Enthusiasm, determination, patience, following regulative principles under the guidance of saintly authorities, and avoiding bad association.

The particular methods for addressing specific bad habits may vary, but these are the fundamental principles and I would like to particularly highlight two key factors that support all the others, and help us stay on track until we completely break free — good association and adopting strong daily practice of devotional activities.

Submission and developing attachment to the good preceptor is the most compelling force that gives leverage to overthrow our deep-rooted bad habits. Srimad Bhagavatam describes, that even lowborn and uncivilized people can come to the highest perfection of life. Once again how we can develop that submission and attachment is by valuing and appreciating very deeply the association of such saintly devotees.
One way of practical expression of such submission is to take up strong devotional practices, (daily chanting, scriptural study etc) which themselves give us determination and keeps us enthusiastic. But beyond that they attract the mercy of the Lord, Who alone can ultimately cleanse all material contamination from within our hearts (SB 1.2.17:). Without the accompanying cultivation of theistic knowledge and positive spiritual practices, other methods to counteract bad habits, as we often see around us, would at best effect a temporary change. Sooner or later the living entity will once again become susceptible to and overwhelmed by material energy.
In short, the process of retraction of bad habits can be summed up as follows: Recognition, Regret, Rectification, and Reinstatement - aided by saintly association and devotional practices.

----As explained by HH Romapad Swami.