How to get rid insecure?

I just got back from interviewed and it was intense. The interviewer gave me intense questions that I make self doubt about myself.

He highlighted the word, hard. "This job is really, really hard. If you can't work, then don't.

Damn. It makes me self doubt and insecure. Then, I questioning myself right now.

I tried to respond positively, despite how he looked doubt on me

Hhhhmmmmmmmmmmm.... ...

PS: I'm looking video in Youtube now. Anyway, you can give any tips from your experiences in the comment section below. Thank you, thank you so much. 🙇‍♀️