No, you must always apply the effect of the card even if that card would hurt you, such as playing the prince with the princess in hand when the other 2 players have handmaidens out. Always having to play the effect of the card is spelled out in the rule book and making a house variant to change that would greatly alter the balance of the game as it would remove the negative side of some of the more powerful cards in the game.
The point of this is that there will be times when playing a card can be very bad for you and that is to balance out the fact that playing a card can be very good for you or at worst neutral most of the time
Love Letter PDF Rules
On your turn, draw the top card
from the deck and add it to your
hand. Then choose one of the two
cards in your hand and discard it
face up in front of you. Apply any
effect on the card you discarded.
You must apply its effect, even if it
is bad for you.
If there are no valid targets because all other players have a handmaiden in play you can still use the card and in most cases nothing will happen.
- Guard - Nothing happens
- Priest - Nothing happens
- Barron - Nothing happens
- Handmaiden - Does not target others
- Prince- You must target yourself and discard your other card
- King - Nothing happens
- Countess - Does not target others
- Princess - Does not target others