I know it sounds blunt and unhelpful, but driving is really the only way to feel better about driving. The more you practice it, the more automatic it becomes, and the better you can focus on anything out of the ordinary. Watch the road ahead, and assume other drivers are distracted. This will make you a very safe driver. Wait for gaps in traffic you know are safe. This will mean some uncomfortably too-long waits, but you'll get better at judging how much time you have.
You'll get much better at every small detail that driving requires (but only if you practice).
Keep in mind how much is invested in safety features. In the unlikely event that you crash, it will probably only be the car that suffers. Fatal crashes happen when people go way too fast for the conditions, and I'm guessing you won't be speeding.