From an authorial standpoint (or even a cinematic one), negative emotions (especially fear) can trigger physical responses that bypass cognitive reasoning; this is a survival instinct; whereas the formation of a positive emotion takes time for values and identification to build. The easiest way past this is tricky for artistic reasons: tropes and well-known symbols can activate the values of previous encodings. But if you overdo it, your work is a hokey pastiche (or deliberately ironic commentary).