Push back a little. You know you won't do anybody any good if you fry.
Boundaries are limits that are always present, spoken or unspoken, honored or overstepped.
Probably because we're literally in each other's face, and it takes conscious effort to work out the healthy boundary thing. Also, the rules aren't as clear as in nature, where animals set boundaries by marking out their unique territory. Get clear on your limits and powerfully express them. For example, take a coworker who has been staying late several evenings each week, and then snaps at you because you aren't. At first you can probably just ignore them, then give a subtle non-verbal hint like glancing at your watch and raising an eyebrow.