Einstein is an extreme example of such a case - when I read his biography the thing that caught me as very interesting is that he was able to immerse himself in physics irrespective of all the problems in terms of not finding a job, his mothers bitter opposition to marrying his first wife etc.You can hardly trick yourself into such concentration.He must be the lucky few who find such deep interesting topics that life is a pleasure even with all the hardships around!
Einstein's sister, Maja, recalled "...even when there was a lot of noise, he could lie down on the sofa, pick up a pen and paper, precariously balance an inkwell on the backrest and engross himself in a problem so much that the background noise stimulated rather than disturbed him."
Source;http://science.nasa.gov/science-news/science-at-nasa/2005/23...