There are stages in parenthood when your children occupy all of your mental time, and when they do, you may find your mind is closed. If before parenthood you found yourself open to contemplate and examine ideas, after parenthood you may find that your ability to do that has shutdown. I found that for certain stages of the life of my child, all of my time was spent either focusing on their care or worrying about them. But then there were stages when they settled down and there was less to worry about and my mind freed up again.
If you are a parent and you find yourself wrapped up in the state of your child, you should believe that that will pass, and while you never stop thinking about them, you will find you think / worry about them less. This is a good thing.