Am 27 Old Indian Male, A Post Graduate In Engineering

am 27 old Indian male, a post graduate in engineering but doing a low grade job in an oil rig. my job have good future and that made me to select this job. am recently married and happy with my wife. the problem with me is i often lose control of my thoughts. my mind start thinking on its own, and allmost all the time it thinks all the negative stuffs. am very fearful to failure and thus i never attempt to take any challenges. i was a hero during my school days with lot of confidence in mind, as years passed i now just turned to be just opposite of what i was then. always feel inferior, and of course at some moments i feel confident and i do wonderful thinks during such periods. now a days my mind thinks only negative thinks whenever it gets free time. i am literally loosing control of it. suggest me what to do..