Offering to help that person you don't like because you know it's right -although excruciating- might just brighten their day. Want to know why? Because your the bigger person.
What I'm trying to get out here is that, you shouldn't just be kind to the people that are kind to you. Not only is that way too easy, but who does that help?
Personally, I strive to make at LEAST one person smile each day, no, not just with my dashing good looks ;) lol, but because of something I did or said that affected them in a positive way.
Now I'm not saying try and please everyone (!) because we all know that's near enough impossible (especially when you have that one hater that always has something negative to say at the tip of their tongue -_-).
But if you see an opportunity to make a positive difference, I say you grab it, put it in a headlock and wrestle it down! I mean, who doesn't want to be a hero for the day?