Maybe obvious, but I lock the doors, close the curtains at night & got a clip to carry my phone on me at all times. I reassure myself that my husband has his cell phone & I can call him if I need to. It does also help me that the police/fire/rescue station is only 100yds away from my house. (Although when the sirens go off, I have to mentally remind myself its not for me & then say a quick prayer for whoever its for).
I also try to find distractions to keep my mind as busy & productive as possible. Talking with a friend, checking emails or systematically going down a checklist of things for me to do, helps too. My husband & I talk the night before & I have a planner where I write down when I can expect him to be gone that day, so there's no suprises, and I can plan my day of when I'll be tackling the "to do" list to pass the time.