I should worry.
( I ( ( should worry ) . ) )
(ROOT (S (NP (PRP I)) (VP (MD should) (VP (VB worry))) (. .)))
There's no reason for me to be concerned.
( There ( ( 's ( ( ( no reason ) ( for me ) ) ( to ( be concerned ) ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBZ 's) (NP (NP (DT no) (NN reason)) (PP (IN for) (NP (PRP me))) (S (VP (TO to) (VP (VB be) (ADJP (JJ concerned))))))) (. .)))