"Somebody just back of you while you are fishing is as bad as someone looking over your shoulder while you write a letter to your girl"

This quote by Ernest Hemingway is a contrast in between 2 activities that need a particular level of privacy and concentration. Fishing and composing a letter to one's girl are both activities that require a particular level of focus and concentration, and Hemingway is recommending that having someone examining your shoulder while you do either of these activities is equally invasive and undesirable. He is stressing the importance of having a particular level of personal privacy and solitude when taking part in activities that need focus and concentration. This quote is a pointer that it is important to appreciate the privacy of others and to give them the space they require to participate in activities that need focus and concentration. It is also a tip that it is very important to be mindful of our own actions and to be familiar with how our presence may be affecting others.