Endorphins were flowing.
( Endorphins ( ( were flowing ) . ) )
(ROOT (S (NP (NNS Endorphins)) (VP (VBD were) (VP (VBG flowing))) (. .)))
My endorphins were flowing.
( ( My endorphins ) ( ( were flowing ) . ) )
(ROOT (S (NP (PRP$ My) (NNS endorphins)) (VP (VBD were) (VP (VBG flowing))) (. .)))