How to get over the fear of driving?

I got my driving license 4 years ago, but I haven't driven since. The reason I didn't drive for all this years is my boyfriend's death; he died in a car crash, and since then I'm scared of driving.
Finally after years I had the courage to start again, so I am taking refreshing classes to gain some confidence. But I am still struggling, even after many lessons.
Every time I get nervous and start to do things wrongly. When driving I constantly worry, because I don't want to hurt anyone, neither I want to cause any accidents.
I just feel like a complete failure, everyone can drive, it's like a normal thing, but I can't.
Any tips?
How to get over the fear of driving?
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