A lot of people keep asking me how I still have the motivation to start a PhD in a totally new department where I have to do classes like Electro Magnetism, Quantum Mechanics and Thermal Physics which I haven't read in over 5-6 years...

well simple answer.... The feeling I get when I work hard on these classes and manage to top at class of 23 students with a 99% on the final is what keeps me going and looking forward to more such things :)