I am retired now, but looking back, the demeanour, attitude and temperament of others in the workplace impacted happiness or otherwise.
There was one person (in another workplace, but one that I frequently visited) always greeted me when I walked in, or if she was unable to do so, would give a welcoming smile or wave and speak later. She was the same with those who worked in her office permanently and generally made people happy. Her attitude seemed to 'rub off' on others and the good feelings were almost infectious.
But I also remember people in the more distant past who would come to work in a bad mood and this also affected others. Although we didn't all end up in a bad mood, the general atmosphere could be tainted. I was nursing on the wards at the time and one old lady patient would always pick up on this and whisper to me "she's got out of the wrong side of the bed!"