Do depressed people know they're depressed? Can I tell if it's starting again or does that mean I'm okay now?

10 years ago in my teens I was diagnosed and treated for depression. It got better and I was eventually off medication and out of therapy and feeling back to my normal self. However, recently some of those same feelings I remember feeling at the beginning of that period of depression have returned and no matter what i do or tell myself I can't make them go away, exactly like last time.

Could this mean i'm starting a period of depression again or does it simply mean i'm NOT depressed because i can spot it?

Thanks in advance for your help.