A party's own act should prejudice himself, not his adversary.

Explanation

(English-origin maxim.) Where one party's conduct creates a legal disadvantage, the burden falls on the actor himself — no man should profit from shifting the consequences of his own deed to another.

Where this applies

• A seller who conceals a known defect in a house cannot later sue the buyer for rescission when the buyer discovers it — the seller's own fraud prejudices only himself.
• A party who misses a filing deadline through his own neglect cannot shift the consequence to his opponent by asking the court to penalize the other side.
• A contractor who walks off a job without finishing cannot sue the homeowner for the remaining payments — his own breach works against him, not the homeowner.