Dissertation stresses

I think one of the biggest mental hurdles for me now being in the dissertation phase of my academic career is that up until this point there are very clear steps you complete. You complete each given assignment for a class. Then you complete a class. Then you complete a series of classes. But now each quarter is not a new class with new assignments to complete but a continuation of the ongoing dissertation process. I realize that there are milestones built into the process for "completion" but its not the same as completing an assignment our a class. There is still more to do and for me it always feels like I need to be doing more. This creates a continuous cycle of stress for me. I am working on developing a way for me to coping with and/or relieving the stress.