Hi. You have stated that you can't study more than one hour and you easily get tired. I don't know if it is typing mistake or what. No one can continuously study for 12 hrs without getting tired. But as a adult you can study 3 hrs with concentration.  First you should do some concentration exercises. You should think anything negatively. Your purpose of study must be a passionate and interesting one. You should not get deviated. Develop your attitude to good intentions and avoid use mobile phones or unwanted talks to read more. Dont allow Ur mind get scattered. If u have a problem talk to someone who will guide u positively boosting Ur confidence.