"If it is possible, as far as it depends on you, live at peace with everyone."
We are not guaranteed to be friendly with everyone. They are going to be people who will not forgive you even if you apologize as well as those who know how to hold a grudge for a lifetime. There are some who will also never treat you they way you want to be treated and people who will discriminate against you. Especially for the Christian, there will be people who downright hate you for trying to speak the truth in love to them for Christ's sake.
There is only so much you can do to pursue reconciliation and forgiveness on your end because it is a two way street, however it is worth doing. Paul is asking us to do whatever is necessary to be at peace, and if peace is not possible, do everything you can. That's really all Jesus ever really asked of you: Do the best that you can. In this way you live without regret.
So don't beat yourself up if people don't like you. There will always be people who don't like you and if you are doing anything worthwhile, having haters is a good sign. Love your haters and don't get mad at them because they do what is only natural to them. Take care of their needs and let God handle the rest. Try and make amends, but if they refuse, then just do what you can.