Great mistake to say too much.
( Great ( ( mistake ( to ( say ( too much ) ) ) ) . ) )
(ROOT (S (NP (NNP Great)) (VP (VBZ mistake) (S (VP (TO to) (VP (VB say) (ADVP (RB too) (RB much)))))) (. .)))
The best thing to do was to say everything they knew.
( ( ( The ( best thing ) ) ( to do ) ) ( ( was ( to ( say ( everything ( they knew ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJS best) (NN thing)) (SBAR (S (VP (TO to) (VP (VB do)))))) (VP (VBD was) (S (VP (TO to) (VP (VB say) (NP (NP (NN everything)) (SBAR (S (NP (PRP they)) (VP (VBD knew))))))))) (. .)))