Everyone starts as a beginner. And as we get comfortable with working out, eventually we learn the basics: how to use the machines, how to observe gym etiquette, and what happens if we don’t wipe the gym equipment. Thank goodness!

But even after you ditched the training wheels, you could still make grave rookie mistakes—those that sabotage your progress and leave you frustrated, confused, and exhausted. Even if you worked out for years, it could still happen. To build an awesome body and take your fitness to the next level, you must avoid these nine worst beginner mistakes. Learn how they happen and how you can beat them.