I interviewed a lady once for a visiting teaching conference. She had been a shut in for a few years, but wrote letters for VT at that point and was a VT supervisor as she could call people. She just had too many health issues due to age to leave the home much if at all.
Anyway, my favorite comment was along the lines of, "Sometimes when you visit people, you click and sometimes...well you don't".
That interview or conversation has always reminded me that sometimes I serve people in church that I don't necessarily like too well or get along with and I do it somewhat begrudgingly. Other times I end up with a new best friend or good friend out of the deal.
I think this is where it is hard for us to do as the article is saying, not due to sins or backgrounds (or at least I hope not), but because it is hard to serve someone we don't 'click' with.