If I had chosen to be an actor, I should have been the greatest actor living! 
( ( If ( I ( had ( chosen ( to ( be ( an actor ) ) ) ) ) ) ) ( , ( I ( ( should ( have ( been ( the ( greatest ( actor living ) ) ) ) ) ) ! ) ) ) )
(ROOT (S (SBAR (IN If) (S (NP (PRP I)) (VP (VBD had) (VP (VBN chosen) (S (VP (TO to) (VP (VB be) (NP (DT an) (NN actor))))))))) (, ,) (NP (PRP I)) (VP (MD should) (VP (VB have) (VP (VBN been) (NP (DT the) (JJS greatest) (NN actor) (NN living))))) (. !)))
I chose to become an actor, but I wasn't very good at it. 
( ( ( ( ( I ( chose ( to ( become ( an actor ) ) ) ) ) , ) but ) ( I ( ( was n't ) ( very ( good ( at it ) ) ) ) ) ) . )
(ROOT (S (S (NP (PRP I)) (VP (VBD chose) (S (VP (TO to) (VP (VB become) (NP (DT an) (NN actor))))))) (, ,) (CC but) (S (NP (PRP I)) (VP (VBD was) (RB n't) (ADJP (RB very) (JJ good) (PP (IN at) (NP (PRP it)))))) (. .)))