11. You Go Heavy All the Time
Even if you’ve set a goal of getting stronger, you should mix things up — do more reps with lighter weight and fewer reps with moderate or heavy weight. Training with heavy weights every time you work out can actually keep you from adding muscle and raise your chance of injury. You might vary your workouts with moderate-, heavy-, and light-weight days.
12. You Don’t Take Water Breaks
Staying hydrated is important for cooling off your body and keeping your blood flowing. Drink water before your workout, then 6 to 8 ounces for every 15 minutes you’re active, then some more once you’re done.