Is it better to practice mindfulness only when I feel good or when anxiety is highest?

I've heard contradictory advice: some say practice when you're calm to build reserves, others say practice when anxiety is highest to cope with the crisis. Which approach is more effective for building long-term emotional regulation and genuinely reducing the severity of my anxiety spikes? My name is Reena, and I am from Delhi. My DOB is 15th April 1994, born at 9:00 AM.