Yin Yin has been in 4 bike accidents and does not wear a bike helmet. Wearing a helmet is important for safety. The document suggests ways for Yin Yin to form a habit of helmet wearing, such as starting small by only wearing a helmet for her first bike ride of the day. Leaving the helmet by the bike each time serves as a trigger to help develop the habit. Establishing the habit with a friend's support can also help reinforce the new behavior.