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 and get a grueling workout in with energy leftover 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? Sure, some of it is due to age. While some people can remain active well into their sixties, and hell some people in their seventies, it’s just a biological fact that we can’t be as energetic as we were back in our early twenties and teenage years.

But don’t blame biology for everything. Chances are there’s probably many things you’re doing, or not doing, that are leading to decreased energy. Whether it’s drinking too much caffeine—put down the Monster—or eating the wrong types of food, there are ways to get some energy back into your gas tank. Luckily for you, we’ve tracked down the most obvious culprits.

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