When something is forbidden, it becomes so much more attractive. That's one serious design flaw with us human beings.
Hot. Do Not Touch
Wet Paint. Do Not Touch
How many times have you ignored the above signs just to see if they're being truthful? When something isn't allowed, I instantly think "yeah, we'll see about that". Perhaps that's the impulsive child in me. Perhaps it's just natural human curiosity, it's a good thing we're not cats.
This can extend into emotions, too. Though to a lesser extent from the impulsive side. Feelings seem stronger when you're not supposed to feel them, during times you're not supposed to laugh everything suddenly becomes so much funnier, the very act of not being allowed to laugh triggers something inside you that you just can't shake away.
Love is the same, at least for me. If you shouldn't have feelings for someone, whether that be because they have a boyfriend or they live on the opposite side of the planet, the mere fact that you can't be with them intensifies those feelings.
I read a study a while back that people who start relationships privately, sneaking around (think work relationships) tend to have the longest, happiest relationships. The feelings they develop for each other are so much stronger because they're not "supposed to" and this to me, is another annoying design flaw.
Why would I fall for someone who I can't be with, as opposed to falling for someone that you can? Why would I touch that wet paint sign?
I'm sure there's a scientific reason behind it, but my god is it annoying.