Some synonyms for "not to worry" are "don't fret," "take it easy," "calm down," "no need to stress," and "don't concern yourself." These phrases all communicate a sense of reassurance and an encouragement to relax and not feel anxious or overly concerned about a situation. They can be useful in a variety of contexts, whether someone is worried about an upcoming exam, a job interview, or a personal relationship. The key is to choose a phrase that feels natural and comfortable to use in your own speech so that you can communicate your supportive message with ease and authenticity.