Completing 10 reps feels like an accomplishment, but sometimes our muscles are too exhausted to finish a full set. Trainers, gym instructors, and even you might push for a complete set of 10, despite your form being off or your muscles screaming in a bad way. Instead of pushing yourself past your limits, do less reps with perfect form to safely improve your strength and endurance and avoid injury. (You may also want to make sure you are lifting the right amount of weight in strength-training exercises.)
To know when you've pushed passed your limit, it's important to recognize the difference between a healthy muscle burn vs. sharp, shooting nerve pain. It may seem like a no-brainer, but my trainer says that no exercise should cause the kind of pain that makes you want to throw up, pass out, or cry. How often have you pushed yourself further even though you intuitively knew that an exercise didn't feel right? So even if you can only complete eight reps, stop before your muscles seize up and rest assured that you are doing your body a favor by not pushing beyond its means. Someday you will work your way toward a perfect set of 10.