This is completely normal when learning any complex task like martial arts. Being anxious about it won’t help. Accept that achieving expertise takes
time and consistency of practise.
Assuming you’re working at 80-90% of your one rep maximum weight, three sets is only OK but your progress will be slow. You need to work up to between 8-12 sets! of 6-10 reps. The last two reps of each set should be hard.
Very good! You
are improving!
I think your issue is in your head. You sound like an anxious person who may have unrealistic expectations of progress. You need to sort out your ‘head game’.
I assume you’re a young person so this is a
reasonable amount of exercise. Just carry on and you will get there even if it doesn’t feel like it!