Why does Otto VOM Bismarck feel it was necessary to avoid doing great harm to Austria in its war against Prussia?

Otto Von Bismarck believed it was strategically advantageous for Prussia to avoid inflicting serious harm on Austria during the war because he wanted to keep Austria as a potential ally in future conflicts and prevent the rise of a powerful anti-Prussian coalition in Europe. By maintaining good relations with Austria, Bismarck sought to weaken potential threats to Prussia's dominance in the region.