I am a junior developer, two weeks ago I got a job for the first time in my life as a fullstack web developer, I have felt bad for the times that "I should have read the code better before coding", I think I am distracted and impatient. I make mistakes because I don't know how the system works in some parts and I write repeated or unnecessary code, my boss has corrected me, but I feel very stupid and I'm afraid of being fired. Is it normal to feel like this?