How to do this at work?

And whatsoever ye do, do it heartily, as to the Lord, and not unto men; Colossians 3:23

Giving my best effort but my attitude really sucks because as advertise Wal-mart is good about asking to much of us employees. Today I happen to be the only one on 2nd shift for 3 departments and after doing marks downs what little time I have left is mostly going to be to clean 2 departments. Honesty very angry about no help and sick of management.

So how can I keep a good attitude when management wants to overwhelm me with this much work?

You'll just have to do what you can and pray that they will appreciate the effort that you put into it. God knows how hard you are trying and He's got your back.

as ZT has said, when we give our very best/heart to everything we do,
we should be doing it as if we were doing it unto/for Christ,
as He is our real employer who blesses us with Real
benefits......

If you like reading.. There's a book by Tim Keller called Every Good Endeavor, approaching work, why we work, and our attitude towards work from a Christian point of view. I thought it was a great read

I understand your frustration. A few years ago I was working at Walmart in the bakery department. It was short-staffed as it was and even then people would call out and you would be alone the whole day and expected by management to do everything regardless by yourself. I was in the process of baking bread one Sunday morning by myself when this manager calls and tells me to drop everything and stock the mini-pies by the registers. Told her I was by myself and at a critical stage of the baking process. She said "so what" stock them anyway. Told her that there were actually no mini-pies left in the freezer to stock. She hung up on me. Screw the mini-pies.

Actually, I believe this also.