Think:
My stomach acid killed the butterflies.

What would you think to kill nervousness?

If it's something like stage fright, probably pretend that I'm just imagining the audience, and I'm actually in my room, 'practicing' whatever I'm doing on stage.
A lot of people around me when I'm not used to small places or because I simply don't like being around many people; pretend I'm happily alone in a wide island somewhere near 'Hawaii', for example.
Talking to a crush; just think of my crush as my buddy and then after school while in my room, realized I talked to my crush and freak out mentally.

Anything else I should cover?

Eating Chocolate Helps

I suggest you to switch your feelings to other kinds of emotions.Whenever I feel nervous,I attempt to persuade myself that the uneasy feeling is just a reaction of overacting my anticipation.After thinking that way,I usually stop feeling nervous.