Pillowcases can be hard on hair. To minimize friction, I suggest silk pillowcases, satin silk pillowcases or if your budget does not allow, then a regular satin pillowcase will do just fine. Satin pillowcases are not terribly expensive and are much worth the price.
Also, bedtime is a very good time to apply oil to your hair. What I like to do is to put a few drops of jojoba oil on my detangled hair from the ears down. Then I brush with a boar bristle brush to evenly distribute the oil. Also, sometimes I like to do a deep oiling. That entails using a large amount of the oil of your choice. I usually use extra virgin olive oil (EVOO) or coconut oil for deep oil soaks.
Some people use satin sleep caps. Personally, I move around to much to ever be able to keep a sleep cap on, and frankly I don't think I'd feel comfortable wearing one, but for those of you who have a lot of damage, or whose hair is fragile, it's a good idea.
How you wear your hair to bed can also help to reduce wear. When my hair is too short to bun, I like to use double braids or a single braid as a bedtime hairstyle.
At the length my hair is now, my favourite bedtime 'do is a bun placed right on top of my head and held with a satin scrunchie. This style is extremely comfortable, as well as being functional and secure. Also, when I take my hair out of the bun in the morning, I have a bit of extra volume, and also, I have no tangles!
So think about protecting your hair at nigh time. It takes almost no time at all, but the rewards can be great.
Here is a photo of my hair deeply oiled and in my sleep bun.