This is an old principle dating back to the beginning of time that can be applied to an incalculable number of situations. This is only common sense: no one can take advantage of their own fault. This is the duty of care that is required of all of us, at all times.
For example, an intoxicated person who falls off their bike cannot blame the barkeeper or brewer for the physical injury they have suffered! Similarly, someone who falls on the sidewalk while wearing stilettos may be partly responsible for their fate, even if the municipality was negligent in the maintenance. In this last example, if the victim has committed a fault, there may be a sharing of responsibility, at the discretion of the court, so that the municipality should bear only part of the damage caused.
In contractual matters, this concept is also applicable. Whoever asks for the cancellation of a contract because of an error may sometimes be challenged that this is an inexcusable error. It is also for this reason that there is no possible recourse in case of injury, save for some exceptions. That is to say that you cannot request the cancellation of a contract under the pretext that you have only paid too much. A diligent person must shop around!
In case of a dispute, your behaviour will be scrutinized and should there be a breach of your duty of care, you could suffer the consequences. Be careful and diligent at all times!