Here’s a great tip from Sadie E. Hulands in 1913: When doing any kind of white work, such as crocheting, lay a piece of dark green cloth on the lap and note the difference. Green is particularly restful to the eyes.
What happens when you get a bit obsessed with your filet crochet project and work on it as much as possible? Your hands cramp up and you get a deep groove in your thread-carrying finger!