Appreciate it.
( ( Appreciate it ) . )
(ROOT (S (VP (VB Appreciate) (NP (PRP it))) (. .)))
I'm forever grateful.
( I ( ( ( 'm forever ) grateful ) . ) )
(ROOT (S (NP (PRP I)) (VP (VBP 'm) (ADVP (RB forever)) (ADJP (JJ grateful))) (. .)))