It's absolutely normal. Change is scary. But as I was taught in college, you don't usually have control over your circumstances, just your responses. You chose this path (this time) but you can't predict whether you and your husband will break up over fights, or whether your child will be damaged or traumatized by some small thing you do. (I think this part might actually be inevitable, nobody can be a perfect parent because they are HUMAN) You can't control whether some horrific tragedy comes your way and takes everything you've built away from you. You can only modulate how you respond to each situation.
Realizing you don't have any real control over the universe beyond yourself, you can then simply do your best to meet the challenges thrown in your direction. Hopefully you don't end up depressed due to your lack of control over the situation. Sometimes it's better to analyze situations according to risk rather than control. That's what I do, at least.