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New millennium astrological chart
In Hindu astrology, Mangal Dosha is an astrological combination that occurs if Mars(Mangal) is in the 1st, 2nd, 4th, 7th, 8th, or 12th house of the ascendant chart. A person born in the presence of this condition is termed a manglik.
It is believed to be unfavourable for marriages, causing discomfort and tension in relationship, leading to severe disharmony among the spouses and eventually to other bigger problems. This is believed to be caused due to the "fiery" nature of the planet Mars, named after the Roman god of war. Also, if two mangliks marry, the negative effects are believed to cancel each other out. However, Mars is not the only planet in Astrology that is supposed to affect the relationship and these effects should be seen in a broader perspective of overall astrological compatibility. 
Why Mangal or Kuja Dosha is considered ‘bad’?
If you are also a victim of Manglik dosha, you’ve probably seen the way facial expressions of many elders change, at the mention of this word. They immediately consider you someone who is lusty, highly short-tempered, rude, aggressive, rough, drunkard, egoist, self-centered, bad at relationships, etc. etc. etc. 
There is a belief that the negative consequences for a single-manglik marriage can be resolved if the manglik first performs a ceremony called a kumbh vivah, in which the manglik "marries" a banana tree, a peepal tree, or a silver or gold idol of the Hindu God Vishnu. However, there is no scientific or theoretical or practical reasoning available to prove it's effectiveness.
The bad effects of Mangal Dosh can be reduced with the help of astrological remedies which would generally include the application of Pooja, Mantras, Gemstones and Charities and these remedies are different for different individuals depending upon their horoscopes.
Myths about Mangal Dosha
Myth 1: There is double or triple manglik
Reality: There is only one planet Mars and hence, one can be either a manglik or not.Neither is there less, medium or high level of dosha.
Manglik and Karma
Most Indian religions are based on the ‘Karma’ theory and clearly state that no one can escape the results of their own karma. The idea of astrology was introduced only to guide and point so you can make wise decisions with respect to your present karma more mindfully. But some astrologers to keep their business running misused it. I don’t know what kind of past karma led you to be blessed as Manglik, but when you are one, why waste the opportunity by running after pundits for ‘curing’ something that’s not even ‘ill’ or ‘evil’. It’s nature. No matter what the permutation combination of stars you consider, only your present will define your future. So why not instead spend that time doing what you love – paint, dance, cook, work, play or write and just Breathe!