Similes:
* "My stomach felt like a swarm of butterflies had taken up residence." (This is a classic simile for nervousness.)
* "My hands were shaking like a leaf in a hurricane."
* "I was so nervous, I felt like I was about to burst into flames."
Metaphors:
* "Anxiety was a tight band around my chest, squeezing the air out of my lungs."
* "My heart pounded like a drum in a frantic tribal dance."
* "Fear was a cold, clammy hand gripping my throat."
Personification:
* "My nerves were on edge, ready to snap at the slightest provocation."
* "Fear whispered doubts in my ear, urging me to back down."
Hyperbole:
* "I was so nervous, I could have jumped out of my skin!"
* "My knees were turning to jelly, and I was about to faint."
The best sentence to use will depend on the specific context and the level of nervousness you want to convey.