If you find your blood boiling every time you inspect a recently vacated property, change your thinking. Remember that, ultimately, your tenants are making you rich. For the entire time they rent from you, they're paying your mortgage, covering your taxes, paying down your principal, and providing you with positive cash flow as your house appreciates. In return, they get a roof over their heads - one you can't expect them to obsessively clean and maintain. More often than not, tenants will take decent care of your property; at least, good enough for them to enjoy living in it. But don't be shocked if, after they move out, your carpet is a little dirty, the walls could use a coat of paint, and the yard needs to be edged. Compared with how much cash your tenants gave you in rent as your home appreciated, fixing that stuff is a small drop in the bucket. At net, you're still way ahead.
Focus on the Big-picture.