Nothing in this universe exists without duality. It is the same for all of us. In other words nothing exists without its opposite. Open eyes and look around. You will start noticing this.
I could bring out few examples as day-night, yes-no, heaven-hell, man-woman etc. Everything has its opposite.
Now you can understand if only we see a part of something. We have not seen the full picture. To see a full picture of somebody/something we need to see the opposite as well. Then you can see totally. That is wisdom.
If we only see one part of anything we are mislead. The day you see it completely is the day you know what it is.
But you/me need to understand that there is nothing wrong with duality. For the things to exist duality is required. For us to experience light, darkness has to be there.
If we name a person very good, the very bad part also in that person. Good and bad in the same percentage. Half-half.
Lord Buddha preached that Middle way is the path. In other words its about finding balance and being in the center.
If you are in the center you can see the both sides of your own self. For example your one part could be light and other half part could be dark. When you are in the middle you will know what to use in which way without any harm to anything/any one.
Duality will not be any matter/issue to you/me when we know where the center and if we are in the center.
Center is the way.