He/she is thanking you because he/she doesn't know any other person as special as you. he/she is thankful for the person that you are. he/she is referring to the kind, caring, attentive things you do for him/her. he/she is showing his/her appreciation. nice compliment!
SO STAY THE SAME, NEVER CHANGE CUS SOMEONE JUST COMPLIMENTED YOU SOMETHING GOOD.
