There are several other idiomatic expressions that can be used in place of "takes a chill pill." For starters, one could say "calm down," "relax," or "take it easy." Another popular phrase is "chill out," which has a more casual vibe. If someone is getting too worked up or anxious, you might suggest they "take a deep breath," "count to ten," or "step back and reevaluate." Additionally, "let it go" and "don't sweat it" are other common phrases that can be used to encourage someone to relax and not get too wrapped up in a situation. Ultimately, there are many ways to tell someone to calm down, and the right phrase will depend on the context and tone of the conversation.