Seeking motivation! Where is it?

I realize after about 30 minutes to an hour and a half that either my motivation or my attention wonders and cannot "put up" with all the words audio or literature. What are some techniques? If I am in control, I usually just pause and exercise. What if that option is not available? I find it almost impossible to sit for 3 hours and listen or read without a break. There has to be little things you can do to re-spark your interests. I guess keep the end in mind by reminding yourself that this is important. The importance sometimes gets pushed aside and I want to just zone out and "recap" on what has been said and take little timeouts to reconstruct the words in my own way. The real world doesn't let you take little breaks does it? What are some pointers?