英文原文見http://www.gocomics.com/garfield/2012/06/03

asustar

transitive verb

1. to frighten, to scare

¡me has asustado! -> you gave me a fright!

me asusta pensar que pueda tener razón -> the scary thing is she may be right

asustarse

pronomial verb

1. to be frightened (tener miedo)

me asusté al verlo -> I got a shock when I saw him

2. to get worried (preocuparse)

no te asustes, seguro que no le ha pasado nada grave -> don't get worried, I'm sure nothing bad has happened to him