At the Bridge Table
Confucius' advise is very applicable at the bridge table. Playing bridge can be an emotionally charged and threatening experience.
Therefore be courteous to all Opponents and be nice to your Partner. Especially after you have made a bad mistake a positive consoling word from your Partner will help you more to recover than all the bridge advise in the world !!   (As a Bridge teacher this is often very hard for me to do. But I keep trying.)

Recent Novices at the table are especially vulnerable, and more than anyone else are likely to make mistakes and occasionally get into an bad contract.
In such case please do not punish them by doubling !
You have absolutely nothing to gain from that (their doomed contract will probably give you a top score anyway), but you do great harm to the Novice's confidence, enthusiasm and determination to learn this game.