If you're just learning, don't worry! Driving isn't as hard as it seems. Driver's ed is a lot less stressful than people make it out to be. I was also worried before the first time I drove. Just relax and go with what you know, it's a lot of common sense stuff. You're just learning how to drive. They know this and are used to it. They might pressure you, but nothing absolutely horrible and it's all to help you get better.
As for swerving, if you're paying attention you shouldn't need to swerve, and if it's not your fault then they obviously won't yell at you for it.
When you're the one driving chances are you won't be as worried about going too fast. The perspective is completely different when you're in control. When it's your first time driving they know you're not comfortable and they won't make you do much in terms of driving fast or with a lot of traffic. Driver's ed is there for you to learn. They don't expect perfection or anywhere near it right away.
Once you drive a little more you'll get more comfortable with everything. Just make sure to practice whenever you can. I didn't drive near enough with my parents when I had my permit, and then when I was out on my own the first few times I was petrified.
Just relax, everyone that you see on the road has gone through the same thing.
