complacer a - to please somebody
despreocupado - happy-go-lucky (native speakers, do you use ser or estar before?)
estar alegre - to be happy
estar animado - to be in high spirits/chipper
estar bien - to be happy/content/satisfied
estar contento - to be happy
estar de buen humor - cheerful
estar encantado/dispuesto - to be happy to (do something usually for someone else)
estar en la cima - to be on top
estar en la gloria - to be in seventh heaven
estar eufórico - to be euphoric
estar feliz - to be happy
estar radiante - to be joyful/beaming/radiant
estar rebosante de alegría - to be brimming with happiness
feliz como una lombriz - happy as a clam
un final feliz - a happy ending
un pensamiento positivo - a happy thought
sentirse tocando el cielo con las manos - to feel on top of the world
ser campechano - to be cheerful (as a person)/friendly
ser campante/fresco - to be a carefree person
ser pizpireto - to be a lively/cheerful person
ser risueño - to be a cheerful person/sunny
sonriente - smiley/cheerful
tener alegría/energía - to have a spring in your step
vivalavirgen/viva la virgen - happy-go-lucky person (españa)