Over the past decade, there has been increasing dialogue about psychiatric illness. While this has been important in reducing the stigma of mental illness, many people have adapted psychiatric terminology into their daily jargon. For example, it is not uncommon to hear people described as "bipolar" if they seem moody or others as having "ADD" if they seem hyper. There is much more, however, to these diagnoses than a casual observation.
The key component in most "disorders" is an inability to function in a way that you previously could. This may mean feeling so sad that you stop socializing or feeling so worried that you are unable to focus on work and your performance slips.
In either scenario there is a noticeable change in your mood and the way you handle day-to-day activities. While it is normal to feel badly now and then, it is abnormal for these feelings to persist for a couple weeks or more. Some disorders, however, develop in childhood or adolescence and have persistently resulted in difficulties adapting to the demands of life, whether that be holding onto friends, keeping a steady job, or doing well in school. In either case, a disorder should be suspected and it would be wise to reach out to your physician for further evaluation.
Bottom line: "Normal" includes a wide range of feelings and behaviors. What is normal for one person may be abnormal for another. So the emphasis should be placed on how well you are doing now compared with what is usual for you.
Another way to think about it is: You do something, it causes you problems, so you do more of it. That's a problem, if it happens over and over again. So for example, you drink, it causes you problems, so you drink more.
Look at the things that make you feel shameful, guilty or "bad." If you can have a talk with someone you trust and is wise about life, it is likely a resolvable problem or a phase. If you feel SO shameful, guilty or bad that you can't talk to ANYONE about it, it is probably something you should take seriously and get help for.
Think of your life as a river that flows, carrying you onward. If you grab onto the side of the river, and refuse to let go, you'll have a terrible time of it. And it is also exhausting.
One final thought: "Normal" is terribly overrated. Adjusting well to a sick society is no evidence of mental health.