Good evening.
These are night guards and your dentist has initiated the correct treatment course. However, these guards are not the end solution for providing relief and will only help in preventing the heavy forces, that you subconsciously apply on your teeth, when you grind them together. These forces are enough to wear out causing sensitivity or even fracture your teeth.
Next Steps
If you are having severe clenching/night grinding also called bruxism, it could be stress and anxiety related. Hence try a bit of stress-management therapy (meditation or talk about it to someone- whatever works for you). That would help in the long run in breaking this habit.
Health Tips
For now, a muscle relaxant would help ease the morning soreness and pain. Although it is recommended best that you get it prescribed by your dentist.
Hoping that helps with your query.
Best wishes
Dr Arpita Dutta