You see the drill, you see the pointy instruments, the vibrations, and the smells. It's all so overwhelming. And no one can blame you. I am a pediatric dental assistant, and I see what the dentist can do to children. It starts early, building the foundation of experience, good or bad, on how you will feel about the dentist for the rest of your life.
With that being said, since I work at the dentist, I should know to not be afraid and to understand that the procedures being done are nothing to be afraid of. However, it runs in my family to be afraid. I believe it is a fear that dates back to the early age of man not wanting to feel vulnerable. When a person comes at you with sharp instruments while you are laying down with your mouth open, that's enough to spark a little uneasiness in anyone.
Here are some settling thoughts: Anything that your dentist does is to help you feel better. They are doctors too. They take an oath to help their patients, and that is their sole job. Especially when it comes to the mouth, if there is something wrong you will know it. So anything that they do will be instant relief to help you feel better. Really the only hard part is getting through any injection they give you.
Secondly, your dentist does not intend to ever make you uncomfortable. If they could take away the noise, the vibrations, and any other thing that makes their patients uneasy, they would. That's why nitrous oxide is used: to make their patients calmer and more at ease to what is going on. This makes the patients feel all around more comfortable.
To close this out, your dentist truly has your best interest at heart. If this is not the same for your dentist then there needs to be evaluating done to ensure that you have the best experience. There are amazing dentists out there. They love their patients and would not be able to do what they do without them. So make a change if needed, but there is nothing to be afraid of at the dentist if you have the right one. This is easier said than done, I know, but these are just some calming thoughts to keep in mind.