The five stages - denial, anger, bargaining, depression, and acceptance - are a part of the framework that makes up our learning to live with the one we lost. They are tools to help us frame and identify what we may be feeling. But they are not stops on some linear timeline in grief.
It is important to feel the anger without judging it, without attempting to find meaning in it. It may take many forms: anger at the health-care system, at life, at your loved one for leaving. Life is unfair. Death is unfair. Anger is a natural reaction to the unfairness of loss.
Learning lessons is a little like reaching maturity. You're not suddenly more happy, wealthy, or powerful, but you understand the world around you better, and you're at peace with yourself. Learning life's lessons is not about making your life perfect, but about seeing life as it was meant to be.