There are two options where a dissertation work can be useful after graduate. First is not to allow dissertation to be transformed into a wide research. Second is to understand the theme of the subject and:
a) to the collect printed matter found,
b) to arrange the collected matters,
c) to put your thinking in that materials
d)dissertation must be written clearly and reachable so anyone who reads the dissertation to get it.
Therefore writing a dissertation means to explain your own ideas and to arrange the printed matter found on that subject. That’s called a method-logical experience. It means to do something which could be useful for other people (students, professors, etc.) when it’s time. If you are able to do your argumentation well you will be able to pick up the printed matter well, too. There is always a first time. If you do it once, you’ll know how to do it again. Time teach us to do things better. But the way you’ve learned how to do it will be the way you know how it works.
At last but not least writing a dissertation is a memory testing. As good as you practice your memory in your youths as better your memory will become in your olds. So if you’re going to train your memory for good it’s better to train it with things that matter and are important for you (as pointed out at http://www.a-mentor.co.uk/services/research-writing/dissertation-writing/).
If you work organized, then there is no stupid dissertation subject. You could get conclusions that would matter, after all, despite the inexplicable subject. When you choose your subject beware to know you want that subject instead your professor to impetrate his. Care about your subject.
It wont be good if you get subject you don’t feel good about it or you don’t get it.