Well, regarding your question on how to relax when going to bed...I suppose accepting your fate and role in the food chain is one way to settle the mind. In general, wildlife should leave You alone if you don't telegraph to them the message of FOOD. So, if a bear came at night and wanted to kill You do you honestly think you could outrun or outwrestle the beast in the dark of night? They can knock your head off with one swipe, climb the trees better than you and run faster than You but in general the beasts (including humans) don't want much of energy sapping activity so history shows us that we can sleep in the woods unbothered.
When I am camping with others I usually wear earplugs - that is pretty cool way to block off worrying sounds of the night. However, it is much better to learn to get used to the creatures of the night...one thing is for sure... a hedgehog or similar small creature makes tons of noise in the quiet of the night. Those sounds usually worry people. A much bigger creature usually makes much much more noise in the woods as they go about. Deer stepping on a dry branch causing a crack in the night is like a gunshot (almost) etc etc...