I’m more nervous crossing the border than anywhere else...the officers are arrogant, bullies, they try to make you feel uncomfortable, and can throw a real fucking into your plans wither you’ve done anything wrong or not.
This is true about US border security officers. I once was denied entry into the US because I had the wrong paperwork (my fault) to bring some commercial samples across the border. The US officers are complete assh***s. My passport was flagged for a few years afterwards. This was all before my Nexus card. In my experience, Canadian border security officers are OK, since they know that you're coming home.
I used to cross the border to the US with my young kids pretty often. I would always instruct (train) them to be at their absolute best behaviour when crossing the border, not to speak until spoken to, and look them straight in the eye when answering any questions.
Your job at the border is to get through... not to go head to head with border officers. Treat them like officers, give them the respect that they want (perhaps not deserve) and get through.