Essential things I´ve learned from opera:

Don´t talk to (or kiss or…) someone in the dark, since they are most likely not the person you think they are.

If you talk to someone you supposedly know, and they don´t answer you back or speak in riddles, again: They are probably someone else in disguise. Or it is actually your wife…

If you want to leave someone, just leave. Do not make appointments to say a”last goodbye”, since this will most likely result in you or the other person getting killed or severely injured.

Do not trust a person:

Who has already once betrayed you and gotten you arrested.
Who offers you a song for free use in a song contest, especially if that person is a cobbler from Nurnberg.
Who claims to be your mother, especially if she is a gypsy…
Who claims to be your father, especially if you grew up in a small house in the woods.
Who claims to be the Devil.
Who claims he wants to marry you after having known you for ten seconds.
Who claims to be the last descendant of the old royal house of Radbod.

Try not to marry/fall in love with/have an affair with:

Your brother, your fiance's father, your fiance's murderer, your husbands brother, your husbands nephew, your own nephew, your husbands boss, your husbands servant, a prophet, a Moor, a Dutchman, a Duke, a fisherman, someone hanging around with the Devil, someone who´s had affairs with more than a thousand women before you, a runaway soldier, a poor soldier, an American officer, a Roman General, a Trojan hero..

In brief: Do not have extramarital affairs and stay away from family members and soldiers of any kind..

If you want to kill someone, including yourself, essential tips include:

Taking an extra look if you intend to throw someone into the fire (or you may risk killing the wrong person).

Do it right away without hesitation and long speeches, or someone may prevent you from doing it (or kill you instead!) while you tell the victim how much you hate him/her.

Do it right away, or you may realize that your reasons for doing it are based on simple misunderstandings.

Making sure your father is not around to disturb you if you intervene in other peoples murdering business.

Try to avoid killing your lover´s father at all means. Better to just escape the scene.

Do it yourself. Do not trust anyone else to do it for you or you may risk inadvertently killing your own daughter. Unless you may command the services of the Devil, though it´s generally not recommended to do business with the Devil.

Do not hang around to watch the person die after you´ve killed him/her. Leave right away or you´ll very likely get caught.

Don´t tell anyone. Really. Don´t tell anyone.

If you are the kind of person likely to develop a guilty conscience afterwards: Don´t do it….

In summary: Going to the opera is far from useless....