Am I a coward? 😫

So I've been doing training to be a waitress for the past few weeks(first timer 😅), got better as time went on, except for today. The card machine went down so we mainly had cash payments. It got busy and at some point I lost some of the money earned today. My boss was going to not hire me but gave me another chance, however I felt I screwed up too many times for her so I decided not to stay.

Many people tell me I shouldn't be too hard on myself for being new​ at this but lately I feel like I can't do anything right. I'm not one to cause a problem for others so I tend to stay in my own bubble.

So I ask again, am I a coward for leaving before I may make it worse?

😥Thanks to any for advice.