Here's why:
* Comparative: Used to compare two things (e.g., "He is taller than his brother.")
* Superlative: Used to compare three or more things (e.g., "She is the tallest person in the class.")
To express different levels of relaxation, you'd use adverbs:
* More relaxed (comparative)
* Most relaxed (superlative)
For example:
* "I am more relaxed after a good walk."
* "This is the most relaxed I've ever felt."