People, whether or not they believe in magic or auras, nevertheless perceive them. Auras can be deliberately charged for a singular purpose, as yours was to the end of intimidating others, but they can also be inadvertently charged with the energy of your most recent spell or incantation.
It's subtle at first, but the more spells you cast, the more powerful it becomes.
People who cast positively-inclined spells regularly will emit auras that are innately pleasing to others. Positivity begets more positivity. These people are perceived as more likable, approachable and trustworthy, and good fortune usually comes to them.
The reverse is true with negatively-inclined spells.
It'd be a stretch to do a full swap with one simple spell. You'll have to work back to that positivity with either routinely positive incantations, or cleansing spells to revert your aura to a neutral state. But if you ask me, it's totally worth it.