In quantitative endeavours e.g. taking a maths exam, aim for perfection.
You might not score 100%, or even 90, and it’s up to you to judge the importance of the endeavour, but why aim for less than perfection?
In qualitative endeavours e.g. selecting a life partner, aiming for perfection is both immeasurable and debilitative.
Aim instead for a very high standard, don’t settle for anything less and don’t listen to your head too much. Listen carefully to your heart, it will tell you when you have reached the desired level.