This one took the longest and had the most head scratching!
There were many times in the first hour when I thought I would give up and pack it away. The excuses went like this - 'it's getting too windy now' and 'it's a complicated subject. I've got the drawing sketched in. I should come back and finish it another day'.
Then my determination set in. I turned down my internal voices, turned up my podcast (Artists helping Artists) and carried on.
Three hours after starting, I was really glad I did it. The sense of achievement is even better when you have doubts to start with, when you get over hurdles. :-)