Earlier quoted context omitted.
Careful with that advice. It might have been good for you, it might be good for a lot of depressive people, but definitely not for all. Before I turned twenty I met two people my age who took your advice and exercised until ambulances had to pick them up (literally). Whatever you do to counter your depression, have a trustworthy, knowledgeable aid at your side: a therapist.
This is an almost absurd criticism ("be careful telling people to sleep, people I know who were depressed followed that advice and slept for 12-14 hours every day"). Let's fix it by being more specific, so we don't accidentally cause any more problems: "daily moderate-intensity cardiovascular exercise" (or, if you prefer, "resistance training 3x week"). Or even, "a healthy level of exercise". I agree that therapy is…
Lots of people have unidentified health issues. Underlying health issues can cause low energy, which can be mistaken for depression.