1) Be Better:
You may already be doing the best, but if you are still catching shit, try to arrive earlier and stay a little later. I know it doesn't sound desirable, I know you want to get the heck up out of there soon as six o'clock comes around. Going the extra mile by staying late or arriving early shows that you are unbothered by the daily antics of those around you. Make sure you double check everything you're doing, so that your employer cannot complain about half-tail work or mistakes. No one is perfect and mistakes will occur, but when they do come ask those around you the proper way to do such activity. It shows that you've acknowledged your mistake and you are trying to perfect it.
2) Change your Mindset
I know easier said than done, but if you stay level-headed your employer won't have a reason to question your character. Yes, he/she may still fuss at you, but just take with a grain of salt. If your employer is always mean or nasty to you just think of them as a hater. Even though, you may never figure out why the smallest question or the simplest questions get you chewed out but thinking of them as a hater is just easy. Honestly, they could be having a bad day or maybe they just aren't as personable as you. Justifying why someone else has a bad attitude isn't what you were hired for so don't worry too much about it.
3) Ignore it
It can be difficult to take your mind off something that you walk into Monday-Friday. Don't let it get under your skin because then you have given someone else power over your emotions. Giving in to the negative energy will cause you a headache that was not in the job description when you applied. One of the biggest reasons to ignore it is the " Leverage". At the end of the day, you can get let go as easily as you were hired. What really sucks is that your employer could say you weren't the best candidate because of your attitude, but really it was them the entire time, so don't do that. Try as hard to keep that smile and if you need to go to the bathroom to take a couple deep breaths and hop on the indeed app to scope out other jobs than do so. Just keep your cool.
Okay, so those were a couple tips that I have come with to get me through some hard days in the workplace, what are yours? But, seriously do not work somewhere where it is mentally draining you, especially if it isn't coming from the things listed in your job description.