D&D occasionally uses morale/passion-type modifiers.
In the original MM, some creatures - dragons, su-monsters - get combat bonuses when defending their young. And berserkers get general combat bonuses due to their "battle lust".
Since 3E, barbarians have received combat bonuses when raging, although in more recent iterations this has been reframed as primal magic rather than raw passion.
It is possible to generalise this idea. Prince Valiant provides an example (from p 23 of the rulebook, under the general heading "Modifiers"):
MORALE
Psychological factors such as love, hatred, faith, loyalty, hope, and even sheer desperation are important in real life. Such factors are reflected by morale modifiers in Prince Valiant, the Storytelling Game. The modifiers may be both positive and negative.
Morale can affect both Brawn and Presence. Apply a modifier of 1 when the emotion or passion is strong in intensity. Apply a modifier of 2 for extremely powerful psychological factors.
The players will enjoy the game more if their acting is rewarded with an occasional positive modifier based on morale factors. The Storyteller must use common sense and his instinct for drama to determine the morale modifier for a particular situation.
For the purposes of storytelling, cowards, liars, and villains should often receive negative morale modifiers, representing guilty terror, apprehensiveness, and general confusion. Heroic characters should sometimes receive positive morale modifiers to represent love, confidence and faith, or other grand emotions.
See the examples of combat below for several situations where love inspires Prince Valiant, giving him a positive modifier for morale.
The extent to which these sorts of modifiers are applied will obviously affect the tone of the play experience.