Has anybody experience something like tat when they workout?

I always lost count for one arm after doing the other arm and i'm really worried that i will have a unsymmetrical physique. Mostly the exercise that i encountered would be one arm lateral raise, dumbbell row. triceps extension and so on. Hence do you all think that a few reps could spoil my physiques? Another thing would be my one arm is stronger than another, and the weaker arm usually makes me feel like i'm not working out properly by jerking or partial reps. Thus i really hate doing one arm exercise or isolation exercise. Lastly, when my legs is not 100% fit, my body will sometimes shake during my back workout where i'm struggling to do the exercise.