It is difficult. It's a lot easier now though. The hardest things for me were having to "co-parent" with an AP and seeing him/his features when I looked at my daughter.I can’t imagine raising an affair child. That has to be so difficult. I’m sorry for what you’ve gone through. People suck.
The sperm donor no longer has parental rights, is out of the picture for the most part, and I adopted my daughter so legally she's mine and no different than my other kids.
And having a biological daughter helped a lot. I thought my oldest daughter had her sperm donors eyes but my 11 month old has the exact same ice blue eye color. So the color didn't necessarily come from him and her eyes aren't a reminder of him anymore.