Am I being impatient in waiting to hear back after an interview?

Hi all, I had a job interview on Thursday for a part time job and I feel like it went well, they asked for my availability which seemed like a good sign to me. At the end of the interview the Hiring M

Hi all, I had a job interview on Thursday for a part time job and I feel like it went well, they asked for my availability which seemed like a good sign to me. At the end of the interview the Hiring Manager let me know that I would either get an email Friday afternoon or Saturday morning at the latest as she said that is when they would have finished their interviews, and she did let me know that I would be contacted regardless of if I got the position. I have seen some things online saying I should send a thank you email to thank them for their time, but is it too late to do it now? Also am I being unreasonable for being worried about not hearing anything back from them? It's currently Sunday for me so I will shoot them an email on Monday thanking both interviewers for their time. Also during the interview there was one question I was not prepared for, it was something along the lines of "what was your biggest failure / a time you made a mistake" and my brain genuinely went blank trying to find an example, I asked if we could circle back to it and I was transparent by letting her know i just could not come up with an example but I by no means think I am perfect, the issue is we never circled back to that. Would that have affected my chances and should I try to salvage it by answering the question in the thank you email or should I just let It go? I apologise for my rambling it's just that it was my first proper job interview and I really want this job. Thanks in advance ☺️