To Be Afraid of Your Own Shadow
If you are afraid of your own shadow, then you are scared of almost everything.
e.g. Maria is a very nervous person. In fact, she is afraid of her own shadow!
To Have Butterflies in Your Stomach
When you are very nervous or scared about a situation, then we say that we have butterflies in our stomachs.
e.g. I have a job interview in one hour and I have butterflies in my stomach!
To Break out in a Cold Sweat
When you get nervous or scared, you often start to sweat.
e.g. In the job interview they asked me some really difficult questions and I broke out into a cold seat.
If something makes you scared or nervous, you can say that it gives you the heebie-jeebies.
e.g. I hate walking through the city at night. There are lots of scary people out and they give me the heebie-jeebies.
To Be a Bundle of Nerves
When somebody is nervous, tense or worried, you can say that they are a bundle of nerves.
e.g. I just saw Lewis in the street. He was on his way to his CAE speak exam and was a bundle of nerves.