What's in a diagnosis?
Diagnosis can be a helpful tool but it can also be stigmatizing, limiting and very misleading. It's understandable that we use diagnosis to communicate aspects of mental health from one professional or institutation to another, or to help explain characteristics of mental health to individuals who are suffering from various symptoms. They are misleading in that no two people are alike in their symptomology, and reducing an individual's mental state to a check list of symptoms is very simplistic and says little about who they really are, and how they might mitigate said symtpoms.
One way to look at mental health is to see everyone on a spectrum which ranges from perfect health (an ideal that does not actually exist) to the most severe and debilitating mental state. We are all on this spectrum. Another essential factor is that our mental states are dynamic, and ever-changing, as opposed to carved into stone, so a person may experience periods of high function at certain stages of their lives and tremendous difficulty at others. All people experience depression and anxiety to some degree at various points in their lives which varies day to day, and moment to moment. Some of us are more prone to these states than others, and some are better at masking these states. The possibilities are endless and no variety of diagnosis will ever suffice to describe an individual.
Manualizing mental health is very useful to both managed health care and pharmaceutical companies who can direct treatment to this diagnosis or that one. If you have this diagnosis you should take these pills and get this kind of treatment for this amount of time. This is a medical model that treats mental illness the same way it would treat a cavity or a broken bone and it's not always effective in the long run. It's true, medications and short-term treatment can be helpful to some individuals, in some circumstances, but it often neglects the person, what their individual needs are, and what makes sense for them.
On the other hand, it can also be a way to normalize someone's condidtion, helping them understand that many people are experiencing similar symptoms. You aren't alone. This can be an incredible relief to you, if you've been feeling you are the only one experiencing these kinds of thoughts and feelings.
In short, a diagnosis is a label that describes a list of symptoms in a manual. It may be a relief to know that many other people share this label wtih you, but in no way should be considered a definition of who you are.