To keep a positive attitude on the job, you should

In my opinion, you should not let your feelings get in the way. For example, if a customer is being rude, don't let it get to you. another ting is, remember that paycheck ;) once that money comes in, you'll be very happy :) hope this helped, have an amazing day :)

To keep a positive attitude on the job, you should look for the good in people and things, not just the bad. 
If you see the good qualities in people, and disregard the bad ones, your life will be healthier because you will be happier. You shouldn't complain all the time because that won't solve anything; there is no perfect company so you can rule out that option immediately; although you may try to encourage others to help you, not everyone will want to.

Keep your hands washed and trash kept in trash cans.