Synonyms for Discreet (same or very similar meaning)
WordNet sense 1 (unobtrusively perceptive and sympathetic):
discerning
WordNet sense 2 (having or showing a sense of what is fitting and considerate in dealing with others):
tactful
WordNet sense 3 (heedful of potential consequences):
circumspect
WordNet sense 4 (careful and sensible; marked by sound judgment):
prudent
WordNet sense 5 (free from ostentation or pretension):
restrained
From the ODE community, based on WordNet
add/edit