This word comprises of two words ‘Atma’ and ‘Chintan’. Atma is what you really are and not what you see yourself as—this would make no sense to a being of kaliyug (the present yug). All you think yourself to be is only the physical form that you see, and this is what the role of kaliyug is—to delude you (bhramit karna).
Let us try and understand how kaliyug has its effect by going back in history, in the times of Yayati itself. (Yayati was the ancestor of kauravas and pandavas) Even after enjoying the pleasures of bhu lok for 4000 years (by exchanging his curse of old age with youth of his son Puru), he was not satisfied and could not believe that 4000 years had passed. So even adharmatma and noble king like Yayati, could not go beyond the svah (swarg) lok.
Shantanu was a descendant of Yayati. He wanted to marry Ganga but she put forth a condition that he must never question any of her actions and the day he broke this promise, she would leave him. Shantanu agreed and the two married. They had seven sons, six of whom were thrown into the ganges by Ganga as soon as they were born. When she was about to do the same to the seventh, Shantanu stopped her and asked her the reason behind this brutal act. Ganga stopped and told him that the seven sons were seven rishis who had been cursed to be born in bhu lok, she was relieving them of the curse by sending them back to where they belong. After this Ganga left Shantanu to fend for the seventh son alone. He grew up to become Devavratta or Bhishma (Devavratta continued to live and it is no secret that his was a life of constant suffering)