Sometimes irritation is exhaustion searching for someone to blame.

When you are depleted, everything requires more than you have, and the mind resolves that shortfall by finding a cause outside itself. The colleague chewing loudly, the partner leaving a cupboard open, the slow website. These are not the reason. They are what irritation reached for because the actual reason, that you are running on nothing, does not present itself as a target.

When small things start setting you off, check the basics before you check the people: sleep, food, how long since you had a genuinely unclaimed hour. Handle those and see whether the irritation survives. Very often it does not, and you will have avoided a fight about the cupboard.