It took me a long time to learn that being nice is not synonymous with being Christlike. I grew up thinking it was important to be nice.
And then, one day as I read the gospels I realized: Jesus was not nice. It isn't that, as the exact representation of God, He is not loving, compassionate, and kind. He is sacrificial to the point of death. But love, true love, is not about being nice. And Christlikeness is centered in God, not in others.
Being nice is about pleasing others: saying what they want to hear, dressing in a pleasing way, doing what they want you to do. That is when people will say you're "nice." When we serve others, we are putting the other person ahead of ourselves and this is a nice thing to do.
In Daniel chapter 5, however, Daniel is called to serve the king and the message he brings is not nice. It is asked for, it is necessary, and he is the only one able to translate God's message, but it is a message of death. It is not what the king, or the people, want to hear. It is not about "fixing" other people's problems or giving false reassurance. It's about allegiance to God in the face of difficulty.
I need to be a person of integrity despite the circumstances. This does not mean that I stand in self-righteous judgement or condemnation--and I have at times--for this is sin. This does not mean that I bow to the desires of others, but that I realize there will be times when serving others requires a boldness and steadfastness that is "not nice."