It's just one of those things, you know that happened.
( ( It ( 's ( ( just one ) ( of ( those things ) ) ) ) ) ( , ( you ( ( know ( that happened ) ) . ) ) ) )
(ROOT (S (S (NP (PRP It)) (VP (VBZ 's) (NP (NP (RB just) (CD one)) (PP (IN of) (NP (DT those) (NNS things)))))) (, ,) (NP (PRP you)) (VP (VBP know) (SBAR (IN that) (S (VP (VBD happened))))) (. .)))
It's not something that just happens.
( It ( ( ( 's not ) ( something ( that ( just happens ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ 's) (RB not) (NP (NP (NN something)) (SBAR (WHNP (WDT that)) (S (ADVP (RB just)) (VP (VBZ happens)))))) (. .)))