You might feel sad, as though you are mourning the loss of a lot of things: your old life, the way your family used to do things, and the good times you won't have together now. It's a lot like grieving when someone close to you has died.
You might be missing the parent you don't see every day, and even missing the parent you do see every day, because he or she is working more, or is really distracted or irritable because of the stress he or she is under.
Sadness is natural, and it's OK to feel sad. But there are things you can do to help yourself feel better.
If the sadness is lasting a long time, or it is getting in the way of your ability to do the things you normally do, get help.