There once was a time when you woke up each morning raring to go, eager to seize the day. You were able to get through a 9 to 5 schedule with energy left over to meet friends for happy hour, go out to dinner, and maybe even enjoy a nightcap. You were tireless. Nothing could stop you. You were a machine! But now… something’s changed.

You’re exhausted by the time you get home. Sometimes it’s hard for you to get out of bed in the morning. Your workouts aren’t what they used to be and the most appealing thing in the world to you is your bed—or your couch, when you can’t even make it to your bedroom to conk out.

What happened? How come you’re so tired all the time?

Here are 11 reasons you have no energy—and what to do to get it back.