When I make mistakes like this, I tend to start over again, but this time I decided to keep going. I will say that the disappointment did cause me to choose more simple patterns than what I was planning. Apparently when I make a mistake, I let it effect me a little more than I should.
Over the years, I have learned to work around the mistakes that I make in a drawing, but I must admit that there's still a part of me that gets annoyed by my own mistakes. What's funny about that is most of the time, no one other than myself would even know that a mistake was made.
This is something that I try to impress upon my students. Even when you think there's a mistake beyond repair, keep going. There's a great possibility that the mistake will not be noticeable once you finish the piece.