Fluttershy many not be the most outgoing pony but she is far from boring. She has one of the biggest hearts and loves to care for the animals in Ponyville. What she might lack in being sociable she makes up with in kindness. She is always looking out for her friends and many others including being nice to Discord.
However, being nice does not mean being a doormat and you shouldn't have to go to extremes to show you're a nice person. You shouldn't have get to the point that you lose your temper after getting flustered and frustrated like Fluttershy when she finally reaches her breaking point after finally letting so many things get to her.
This challenge is for those who maybe a little too nice and they let others walk all over them. I used to be like this back in middle school but after a while I realized that's not who I wanted to be. I'm still nice but I'm no pushover. I stand up for myself and not let others take advantage of me. And that's the best advice I can give.