When you say a vow, you cannot guarantee the future, and when you express regret, you cannot change the past. They can only express an emotion or thought at the moment. In linguistics, each other's vows are a rhetorical technique called exaggeration. The rhetorical technique is subjective and exaggerates the current emotions and thoughts rather than portraying objective facts.
Concept: Realistic love, if you are in love, you will be beaten to death.