sincere vs heartfelt

sincere and heartfelt both are adjectives.

Word	Noun	Adjective	Verb	Adverb
sincere	No	Yes	No	No
heartfelt	No	Yes	No	No

sincere (adjective)	heartfelt (adjective)
open and genuine; not deceitful	sincerely earnest
characterized by a firm and humorless belief in the validity of your opinions