I know I'll have to say "no," but I think it's good to use positive language when possible. I think it gives more weight when you really have to say "no." Plus it's a bummer for kids to hear "no" all the time.
Time-outs are used to punish and shame, but a calm-down helps kids deal with intense emotions. Calm-downs are a healthy and positive discipline approach for both parents and children. Love this guide for parents!