How many lessons have you had?
Is your instructor quite calm and patient how do they handle mistakes?
Is there something that makes you particularly anxious about lessons?
I found driving on busy traffic made it worse for me so I moved my lessons to 9:30 when it's less, it meant I could concentrate more on what was in front then worrying about how many people I was holding up.
It's also worth discussing it with your instructor as they might have suggestions?