How to ensure accuracy while performing repetitive tasks?

Thanks 

You have to follow the next steps 

• Numerical achievements to ensure that you hit your goal
• Put a mile stone to know when and where you need to stop and what phase you need to review
• Make a review every end of any phase 

Keeping focus and by understanding the problems caused by your casual behavior to others. 

1. I assume you are talking of a Physical task
2. Scheduled and Random Breaks are extremely necessary.  Shceduled breaks alone are not advisable as the body may treat these breaks also part of the repetitive tasks.  Hence random unplanned breaks also are necessary to break the repetitive cycle of the body.  The brain and the body, both, need to disconnect at times to break the cycle
3. If it is a physical task, then You need to be aware of any WRULDs (Work Related Upper Limb Disorders) and RSIs (Repetitive Strain Injuries) so kindly read it over the net
4. You need to raise a flag if there is any physical or mental strain / stress you develop while doing the task however small it maybe and consult a doctor
5. If it is a numerical mental activity, then you need to disconnect from it every 45 minutes for 5 minutes