Everyone has a public side that they show to everyone, and a private side that is only shown to their most intimate friends (and sometimes, not even to them!). So what about your characters?
There is a difference between a character trait and a character persona. Your characters, just like real people, will have certain traits that they wish to keep hidden. They have certain facets of their personality that they will strive to disguise. And that can give you a great source of conflict and tension.
Think about people you know: the beefy muscle-man who’s petrified of needles, the soccer mom who runs marathons, and the bespectacled professor-type who’s a secret underwear model. Don’t we all have our hidden sides? Shouldn’t your characters have one as well?
Give your characters some secrets, preferably ones that they either don’t want known, or that aren’t immediately obvious. Perhaps they’re battling their own dislikes when they serve at that soup kitchen line, or perhaps that jock would really rather be reading a good book instead of making that basket.
The fun of a good story is finding characters who seem to leap off the page, and they can’t do that if they’re just cardboard cut-outs.