> It should not be difficult to be a nice person all the time.

There's a huge difference between most of the time and all of the time.

I'm a strong advocate of empathy in the workplace, but part of that is recognising that sometimes people are just in a bad mood.

Someone who snaps at you because they're really stressed that day is in no way a bully.

If you snap at someone because you are having a bad day you should apologise to that person or at least clarify that it's not personal.

Having a bad day is not an excuse to be rude to someone, especially if they are not aware of that.

What do you do when you're in a bad mood and you blow up on someone?

You apologize the next day / whenever you calm down. And then that out-of-character event doesn't end up being someone's lasting impression of you.

As always, the last 5% is the hardest part.

> It should not be difficult to be a nice person all the time.

I agree, it shouldn't be difficult, but some people seem to go out of their way to make it difficult.