Joy, Liz...Thank you. You are both very kind.
I use to sketch very deliberately, trying to get every detail down exactly as it was. On a few occasions, out of sheer necessity, I sketched very quickly. I liked the result very much. After that, I frequently tried to sketch quickly. This forces you to quickly choose what is essential, and leave out whatever is not that important. Initially this may feel challenging, but soon your results will get better and better.
I feel that I still have a long way to go, but I am happy with the progress that I have made so far.