You can have depressive illness without really feeling depressed. If you don't feel real depressed or suicidal, but everything else in your life is wrong, you may have unrecognized depressive symptoms.
Symptoms vary on an individual basis.
Not everyone who has depression has every single symptom. I'd just say, it's easy to overlook and mistakenly attribute to lack of personal character or initiative. Although there are specific clinical types of depression you may or may not fit into one of the slots. Learn about depression, check out the symptoms. Learn about the treatments for mild to moderate depressions.