Will I ever feel prepared?!?!?!

Seasoned nurses, step in. I'm a new nurse on my first official week on my own. During this time, I've made a some mistakes but the biggest was that I forgot to bed alarm a patient--who left her bed, but didn't fall. She pulled out her iv in the process while I was with another patient...I was called into her room to discover half of my new team cleaning up a bloody mess. Of course this happened on my first night on the unit floor. Everyone was very professional but I felt as though I just became the most unpopular gal in the room.
I'm also working nights which is a huge change for me and a challenge since I'm already sleep deprived (I have a 3 year old and a 3 month old at home).

Anyways, at the end of my shift, hours later, at home I begin second guessing my interventions and convince myself that I've managed to kill all of my patients. "Did I REALLY check x-ray placement of that NG tube before I instilled meds?" "Am I absolutely sure that I clamped off that triple lumen Central Line or is my patient going to get an air embolism?" "Maybe that stomach pain was really epigastric pain related to cardiac arrest and I overlooked it!!" Of course, this paranoia doesn't set in until I think of all the mistakes that I made during my shift. It doesn't matter that I've followed protocol and reviewed the charts, those thoughts just keep popping up.

So seasoned nurses, how long did it take before you started to feel like you were in your comfort zone and felt like you knew what you were doing? And what did you do to help