There's always something to worry about and things that are not going well in our lives. I use those things as kind of "fillers" looking at the bigger picture and realizing "eventually" I will want these things so might as well doggedly work on them now. I try to scrap the worry, march more to the beat of my own drums telling me what I want to learn of this stuff, how hard I want to study it (get a "C" in things you don't care much about instead of trying for an "A" for example) and figure out ways to study while working on your car (listen to lectures? books on tape?), etc.