First of all be thankful for every day. Yes you were fortunate, but take this opportunity after you have a day or two to calm down, but while its still fresh in your mind to go over and review what happened. No it wasn't your fault. You were hit. Yet was there anything you could do to lesson the risks next time. Things that may have made no difference what so ever in this case, but might next time. Do you ride with tail lights on during the day? Do they blink? Is there a safer route to get where you wanted to go? Is there a better time of day if practical? You may not find anything that you would do differently, but go through the process. Once you have learned all you can from the crash, that IS your closure. Let it go. This risks are exactly the same now as they were before the crash. You may ride the rest of your life and never have another problem, or it can happen your next ride, but riding in fear is no fun. Forget the driver. They may never catch them, and either way its beyond your control. Being mad, p o ed and upset is normal. You can't control getting hit, but you can control how you feel about getting hit.
You did a lot right too. Part of the reason you are still here is the helmet. Anyone that doesn't think a helmet is necessary should look at that video of the cracked helmet. It did its job. You are going to be sore tomorrow, but thankfully that's all.