In Bridge, Which Forms of Deception Are Ethical? Does This Include "Moodying?"
"Deception" is a weird concept in bridge.  Just like in every game, there are forms that are ethical and forms that are not.

Falsecarding, as in your example, is perfectly fine.  Your opponent failed to count trumps correctly, and paid the price.  A similar, and perfectly valid strategy, is to play a high card instead of a low card when losing a trick as declarer to make the opponents think that you are now void in the suit, hoping that they will switch to a different suit.

"Moodying" is more of a gray area, and should probably be avoided.  Granted, any information that your opponents take from your tells is at their own peril, but if your partner could use any information that your tell gives away to his and your benefit, then your opponents could rightfully claim to have been wronged.

Very broadly speaking, deception is OK as long as you are deceiving everyone at the table, partner included.