You develop sleep problems.
This can be either insomnia or you sleep longer hours. Even after a long night in bed you still crave more sleep. You have no energy and feel like you could spend a full day in bed.
Your weight changes.
You suddenly gain some pounds or lose weight. You could also develop an enormous appetite and feel constantly hungry regardless of how much you eat. Or you stop feeling hunger at all.
Nothing brings you pleasure.
Even the things, activities, and people you used to love do not add joy to your life. You are constantly bored, tired, and have no desire to do your life-long hobby or meet your best friend.