People aren't very good at guessing how close they are to muscle failure when doing many reps of weightlifting.

When people lift weights until they're almost too tired to continue, especially with arm exercises, they get better at guessing how many more reps they could do. It's like training your body to feel its limits more accurately.

If you're lifting weights and want to see real gains, pushing yourself to failure only works if you're using heavy weights and doing enough sets and reps. If the weight or volume is too low, it probably won't help much.

When people who are already fit push themselves as hard as they can during weight training, it doesn't matter if they lift heavy weights for a few reps or lighter weights for many reps—both ways build muscle about the same.

Whether you lift lighter weights or heavier weights until you can't do any more reps, both ways give you the same muscle growth and strength gains if you're already used to training.

Whether you lift light weights many times or heavy weights fewer times—both can make you stronger in exercises like squats and deadlifts, as long as you push to exhaustion.