You probably aren't used to having a lot of boundaries with your spouse. Unfortunately, redefining your personal boundaries is a part of moving forward, and there's simply no way to achieve a healthy divorce without them.
Addiction doesn't just affect the addict -- it affects the addict's entire family. If your spouse has a substance abuse problem and is addicted to drugs or alcohol, at what point do you decide that you can't stay married any longer?
Divorce can be a painful, emotional process. Often, parties fight; they face financial obstacles; they might say hurtful things about each other inside and outside the legal setting.