upbeat vs successfulness

upbeat and successfulness both are nouns.

Word	Noun	Adjective	Verb	Adverb
upbeat	Yes	Yes	No	No
successfulness	Yes	No	No	No

As nouns, successfulness is a hypernym of upbeat; that is, successfulness is a word with a broader meaning than upbeat:

Other hypernyms of upbeat include prosperity.

upbeat (noun)	successfulness (noun)
an unaccented beat (especially the last beat of a measure)	the condition of prospering; having good fortune
a contented state of being happy and healthy and prosperous

upbeat (adjective)	successfulness (adjective)
pleasantly (even unrealistically) optimistic