manage to keep things interesting 
(ROOT (S (VP (VB manage) (S (VP (TO to) (VP (VB keep) (NP (NNS things)) (S (ADJP (JJ interesting)))))))))
(ROOT (S (VP (VB ) (S (VP (TO ) (VP (VB ) (NP (NNS )) (S (ADJP (JJ )))))))))