Their world is mostly not-their-choice
Wake up, get dressed, eat this, get in the car, sit still. Kids are told what to do all day. Pushback is often just a small human trying to feel like a person, not a puppet.
Choices are the release valve
Two real choices — 'red cup or blue cup,' 'shoes on the porch or shoes in the car' — hand back a slice of control without giving up the outcome. Both options should be things you can live with.
Avoid the ultimatum trap
'Do it or else' backs them into a corner where they have to choose defiance to keep their dignity. You can be firm AND leave them a way to say yes.
Save your no's for the real ones
If everything is a battle, nothing is a boundary. Look at your day and ask: what actually matters to me? Safety, kindness, honesty — those are non-negotiable. The color of the shirt, the order of the routine, whether they eat the peas first or last — hand those back.