That feeling of fear never stops. I still hate my step children having anything to do with the OW. My own children do not, but the boys have to. What can I say? I've just been their step-mom for 20+ years. And the grandchildren. THAT's a whole other bucket of worms.
I know I have no reason to be insecure about their feelings for me, but doing so just makes me human.
You have to wonder how the H tolerates his children being done that way. They are so blind!